<p>As opposed to data types such as <code>int</code>, <code>bool</code>, <code>float</code>, <code>str</code>, a list is a <strong>compound data type</strong> where you can group values together. In Python, it would be inconvenient to create a new python variable for each data point you collected. What you can do instead is, store all this information in a Python list. You can build such a list with square brackets.</p>
<pre><code>[a, b, c]
</code></pre><h2 id="building-a-list">Building a List</h2>
<p>Suppose you asked your two sisters and parents for their height, in meters. You can build the list as follows:</p>
<pre><code class="lang-python">[1.73, 1.68, 1.71, 1.89]
</code></pre>
<pre><code>[1.73, 1.68, 1.71, 1.89]
</code></pre><p>Of course, all this data can be referenced to with a variable. Simply, put the variable name and the equal sign in front, like here.</p>
<pre><code class="lang-python">fam = [1.73, 1.68, 1.71, 1.89]
fam
</code></pre>
<pre><code>[1.73, 1.68, 1.71, 1.89]
</code></pre><p>A list is a way to give a single name to a collection of values. These values or elements can have any data type; int, float, etc., and also more advanced Python types, even other lists.</p>
<h2 id="storing-variables-in-lists">Storing Variables in Lists</h2>
<p>It is also possible for a list to contain different types within it as well. Suppose you wanted to add the names of your parents and sisters to the list so you know which heights belong to whom. You can throw in some strings without issue.</p>
<pre><code class="lang-Python">fam = [&quot;liz&quot;, 1.73, &quot;emma&quot;, 1.68, &quot;mom&quot;, 1.71, &quot;dad&quot;, 1.89]
fam
</code></pre>
<pre><code>[&#39;liz&#39;, 1.73, &#39;emma&#39;, 1.68, &#39;mom&#39;, 1.71, &#39;dad&#39;, 1.89]
</code></pre><p>That&#39;s not all though, you can also create smaller sublists inside of a list.</p>
<h2 id="list-inside-of-a-list">List Inside of a List</h2>
<p>In the below example, the small lists are wrapped inside of square brackets and separated by a comma inside a list <code>fam2</code>. When you print the list <code>fam2</code> you see that we have a list of lists. The main list contains 4 sublists:</p>
<pre><code class="lang-Python">fam2 = [[&quot;liz&quot;, 1.73],
        [&quot;emma&quot;, 1.68],
        [&quot;mom&quot;, 1.71],
        [&quot;dad&quot;, 1.89]]
fam2
</code></pre>
<pre><code>[[&#39;liz&#39;, 1.73], [&#39;emma&#39;, 1.68], [&#39;mom&#39;, 1.71], [&#39;dad&#39;, 1.89]]
</code></pre><p>You can also check the data type of lists. Here we will see what type both <code>fam</code> and <code>fam2</code> are:</p>
<pre><code class="lang-Python">type(fam)
</code></pre>
<pre><code>list
</code></pre><pre><code class="lang-Python">type(fam2)
</code></pre>
<pre><code>list
</code></pre><p>These calls show that both <code>fam</code> and <code>fam2</code> are in fact lists. Each data type has a specific functionality and behavior associated with it. This is true for Python lists. They host a bunch of tools to subset and adapt them.</p>
<h2 id="interactive-example-of-list-creation">Interactive Example of List Creation</h2>
<p>In this example, say after measuring the heights of your family members, you decided to collect some information on the house you&#39;re living in. The areas of the different parts of your home can be stored as separate variables for now.</p>
<p>You will create a list named <code>areas</code>, that contains the area of the hallway (<code>hall</code>), kitchen (<code>kit</code>), living room (<code>liv</code>), bedroom (<code>bed</code>), and bathroom (<code>bath</code>) in this order. Use the predefined variables. Finally, you will Print <code>areas</code> with the <code>print()</code> function.</p>
<pre><code class="lang-Python"># Area variables (in square meters)
hall = 11.25
kit = 18.0
liv = 20.0
bed = 10.75
bath = 9.50

# Create list areas
areas = [hall, kit, liv, bed, bath]

# Print areas
print(areas)
</code></pre>
<p>When you run the above code, it produces the following result:</p>
<pre><code>[11.25, 18.0, 20.0, 10.75, 9.5]
</code></pre><p><a href="https://campus.datacamp.com/courses/intro-to-python-for-data-science/chapter-2-python-lists?ex=2">Try it for yourself</a>.</p>
<p>To learn more about creating lists, please see this video from our course <a href="https://campus.datacamp.com/courses/intro-to-python-for-data-science/chapter-2-python-lists?ex=1">Introduction to Python</a>.</p>
<iframe width="560" height="315" src="https://www.youtube.com/embed/MwyD9PmyW3k" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

<p>This content is taken from DataCamp’s <a href="http://www.datacamp.com/courses/intro-to-python-for-data-science/">Introduction to Python</a> course by Hugo Bowne-Anderson.</p>


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(Tutorial) Python Lists

Python Lists

<p><code>.lower()</code> is a built-in Python method primarily used for string handling. The <code>.lower()</code> method takes no arguments and returns the lowercased strings from the given string by converting each uppercase character to lowercase. If there are no uppercase characters in the given string, it returns the original string.</p>
<h2 id="-str-lower-method"><code>.str.lower()</code> method</h2>
<p>In the below example, we will use the <code>.str.lower()</code> method which turns all column entries into lowercase characters. Here is what the list looks like to start with:</p>
<pre><code>            name      price_usd
0          Apple           0.88
1         Banana           0.23
2         Orange           0.68
3     Watermelon           3.98
4           Plum           0.96
5    Blueberries           5.16
6    Dragonfruit           5.27
7           Kiwi           1.12
</code></pre><p>Now, select the <code>name</code> column from the <code>fruit_price</code> dataframe and apply <code>.str.lower()</code> to convert the <code>name</code> column entries into lowercase, as shown below.</p>
<pre><code class="lang-Python">fruit_price[&#39;name&#39;] = fruit_price[&#39;name&#39;].str.lower()

print(fruit_price)
</code></pre>
<pre><code>            name      price_usd
0          apple           0.88
1         banana           0.23
2         orange           0.68
3     watermelon           3.98
4           plum           0.96
5    blueberries           5.16
6    dragonfruit           5.27
7           kiwi           1.12
</code></pre><h2 id="interactive-example-of-str-lower-">Interactive Example of str.lower()</h2>
<p>In this example, all you need to do is use the right method to change the <code>movie_title</code> column to lower case using the <code>.str.lower()</code> method.</p>
<pre><code class="lang-Python"># Change movie_title column to lower lower case
movies[&#39;movie_title&#39;] = movies[&#39;movie_title&#39;].str.lower()

# Look at the change
print(movies)
</code></pre>
<p>When you run the above code, it produces the following result:</p>
<pre><code>                       movie_title movie_genre  movie_length
0              the sumif all fears      Action           124
1             the seaborn identity      Action           119
2                     the matrices      Action           136
3  there&#39;s something about merging      Comedy           119
4                    mamma median!      Comedy           108
5                    harry plotter        Kids           159
6                   kung fu pandas        Kids            92
7           while you were sorting     Romance           103
8      10 things i hate about unix     Romance            97
</code></pre><p><a href="https://campus.datacamp.com/courses/python-for-spreadsheet-users/working-with-multiple-sheets?ex=6">Try it for yourself</a>.</p>
<p>To learn more about putting pandas dataframe together in Python, please see this video from our course <a href="https://campus.datacamp.com/courses/python-for-spreadsheet-users/working-with-multiple-sheets?ex=5">Python for Spreadsheet Users</a>.</p>
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<p>This content is taken from DataCamp’s <a href="https://learn.datacamp.com/courses/intermediate-python-for-data-science">Python for Spreadsheet Users</a> course by Chris Cardillo.</p>


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(Tutorial) Lowercase in Python

Lowercase in Python

<p>Dictionary is a built-in Python Data Structure that is mutable. It is similar in spirit to List, Set, and Tuples. However, it is not indexed by a sequence of numbers but indexed based on <code>keys</code> and can be understood as associative arrays. On an abstract level, it consists of a <code>key</code> with an associated <code>value</code>. In Python, the Dictionary represents the implementation of a <code>hash-table</code>.</p>
<h2 id="what-are-keys-">What are keys?</h2>
<p>As shown in the figure below, keys are immutable ( which cannot be changed ) data types that can be either strings or numbers. However, a key can not be a mutable data type, for example, a list. Keys are unique within a Dictionary and can not be duplicated inside a Dictionary. If it is used more than once, subsequent entries will overwrite the previous value.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1595447333/pydict3_v1tdmd.png" /></center>

<p><code>Key</code> connects with the <code>value</code>, hence, creating a map-like structure. For example, remove keys from the picture; all you are left with is a data structure containing a sequence of numbers. Dictionaries, therefore, hold a <code>key: value</code> pair at each position.</p>
<p>A Dictionary is represented by a pair of curly braces <code>{}</code> in which enclosed are the <code>key: value</code> pairs separated by a comma.</p>
<h2 id="creating-a-dictionary">Creating a Dictionary</h2>
<h3 id="syntax">Syntax</h3>
<p>As a refresher, here is a recipe for creating a Dictionary:</p>
<pre><code>my_dict = {
  &quot;key1&quot;:&quot;value1&quot;,
  &quot;key2&quot;:&quot;value2&quot;
}
</code></pre><p>In the above syntax, both the keys and the values are strings.</p>
<h3 id="example-of-creating-a-dictionary">Example of Creating a Dictionary</h3>
<pre><code class="lang-python">pop = [30.55, 2.77, 39.21]

countries = [&quot;afghanistan&quot;, &quot;albania&quot;, &quot;algeria&quot;]
</code></pre>
<p>Let&#39;s convert the population data to a Dictionary. To create the Dictionary, you will use the curly brackets. Next, inside the brackets, you will have a bunch of key:value pairs. In this case, the keys are country names, and values are the corresponding populations.</p>
<p>The first key is Afghanistan, and its corresponding value is 30.55. Notice the colon that separates the key and value pair. Let&#39;s do the same for the other two key:value pairs and store the result in the variable <code>world</code>.</p>
<p>Now, to find the population for Albania, simply type <code>world</code>, and then the string Albania inside square brackets. In other words, you pass the key in square brackets and get the corresponding values.</p>
<pre><code class="lang-python">world = {&quot;afghanistan&quot;:30.55, &quot;albania&quot;:2.77, &quot;algeria&quot;:39.21}

world[&quot;albania&quot;]
</code></pre>
<pre><code>2.77
</code></pre><p>This approach is not only intuitive, but it is also very efficient because Python can look up these keys very fast, even for huge dictionaries.</p>
<h2 id="interactive-example-of-creating-a-dictionary">Interactive Example of Creating a Dictionary</h2>
<p>In the below example, you will use the strings in <code>countries</code> and <code>capitals</code>, create a Dictionary called <code>europe</code> with 4 key:value pairs. Here the <code>countries</code> will be the keys, and <code>capitals</code> will be the values. Beware of capitalization! Make sure you use lowercase characters everywhere. Finally, print out <code>europe</code> to see if the result is what you expected.</p>
<pre><code class="lang-python"># Definition of countries and capital
countries = [&#39;spain&#39;, &#39;france&#39;, &#39;germany&#39;, &#39;norway&#39;]
capitals = [&#39;madrid&#39;, &#39;paris&#39;, &#39;berlin&#39;, &#39;oslo&#39;]

# From string in countries and capitals, create dictionary europe
europe = {&#39;spain&#39;:&#39;madrid&#39;, &#39;france&#39;:&#39;paris&#39;, &#39;germany&#39;:&#39;berlin&#39;, &#39;norway&#39;:&#39;oslo&#39;}

# Print europe
print(europe)
</code></pre>
<p>When you run the above code, it produces the following result:</p>
<pre><code>{&#39;norway&#39;: &#39;oslo&#39;, &#39;germany&#39;: &#39;berlin&#39;, &#39;france&#39;: &#39;paris&#39;, &#39;spain&#39;: &#39;madrid&#39;}
</code></pre><p><a href="https://campus.datacamp.com/courses/intermediate-python/dictionaries-pandas?ex=3">Try it for yourself</a>.</p>
<p>To learn more about dictionaries in Python, please see this video from our course <a href="https://campus.datacamp.com/courses/intermediate-python/dictionaries-pandas?ex=1">Intermediate Python</a>.</p>
<iframe width="560" height="315" src="https://www.youtube.com/embed/WM-RRXpTku8?start=102" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

<p>This content is taken from DataCamp’s <a href="https://learn.datacamp.com/courses/intermediate-python-for-data-science">Intermediate Python</a> course by Hugo Bowne-Anderson.</p>


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(Tutorial) Python Dictionaries

Python Dictionaries

<p><code>if…elif…else</code> are conditional statements that provide you with the decision making that is required when you want to execute code based on a particular condition.</p>
<p>The <code>if…elif…else</code> statement used in Python helps automate that decision making process.</p>
<h2 id="if-condition">if condition</h2>
<p>The <code>if</code> condition is considered the simplest of the three and makes a decision based on whether the condition is true or not. If the condition is true, it prints out the indented expression. If the condition is false, it skips printing the indented expression.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594834339/ifelse2_yz0cpv.png" /></center>

<h3 id="example-of-if">Example of if</h3>
<p>Suppose you have a variable <code>z</code>, equal to 4. If the value is &#39;even&#39;, you will print <code>z</code> is &#39;even&#39;. You will use modulo operator 2, which will return 0 if <code>z</code> is &#39;even&#39;. As soon as you run the below code, Python will check if the condition holds. If True, the corresponding code will be executed.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594834339/ifelse3_z8utoj.png" /></center>

<h5 id="example-of-multiple-lines-inside-if-statement">Example of multiple lines inside if statement</h5>
<p>It is perfectly fine to have more lines inside the <code>if</code> statement, as shown in the below example. The script will return two lines when you run it. If the condition is not passed, the expression is not executed.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594834339/ifelse4_r0ol8n.png" /></center>

<h5 id="example-of-a-false-if-statement">Example of a False if statement</h5>
<p>Let&#39;s change the value of <code>z</code> to be odd. You will notice that the code will not print anything since the condition will not be passed, i.e., False.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594834339/ifelse5_pnj5hj.png" /></center>

<h2 id="if-else-condition">if-else condition</h2>
<p>The <code>if-else</code> condition adds an additional step in the decision-making process compared to the simple <code>if</code> statement. The beginning of an <code>if-else</code> statement operates similar to a simple <code>if</code> statement; however, if the condition is false, instead of printing nothing, the indented expression under <code>else</code> will be printed.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594834340/ifelse7_cnbil5.png" /></center>

<h3 id="example-of-if-else">Example of if-else</h3>
<p>Continuing our previous example, what if you want to print &#39;z is odd&#39; when the <code>if</code> condition is false? In this case, you can simply add another condition, which is the <code>else</code> condition. If you run it with <code>z</code> equal to 5, the condition is not true, so the expression for the else statement gets printed out.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594834339/ifelse6_yybp5a.png" /></center>

<h2 id="if-elif-else-condition">if-elif-else condition</h2>
<p>The most complex of these conditions is the <code>if-elif-else</code> condition. When you run into a situation where you have several conditions, you can place as many <code>elif</code> conditions as necessary between the <code>if</code> condition and the <code>else</code> condition.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594834340/ifelse8_iruubk.png" /></center>

<h3 id="example-of-if-elif-else-condition">Example of if-elif-else condition</h3>
<p>Below is an example of where you want different printouts for numbers that are divisible by 2 and 3.</p>
<p>Here, since <code>z</code> equals 3, the first condition is False, so it goes over to the next condition. The next condition does hold True. Hence, the corresponding print statement is executed.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594834340/ifelse9_nk5ugf.png" /></center>

<h3 id="example-of-if-elif-else-condition">Example of if-elif-else condition</h3>
<p>In the below example, you define two variables <code>room</code> and <code>area</code>. You then construct <code>if-elif-else</code> and <code>if-else</code> conditions each for <code>room</code> and <code>area</code>, respectively.</p>
<p>In the first condition, you check <code>if</code> you are looking in the kitchen, <code>elif</code> you are looking in the bedroom, <code>else</code> you are looking around elsewhere. Depending on the value of the <code>room</code> variable, the satisfied condition is executed.</p>
<p>Similarly, for the <code>area</code> variable, you write an <code>if</code> and <code>else</code> condition and check whether the <code>area</code> is greater than 15 or not.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594834340/ifelse1_vienhl.png" /></center>

<p>When we run the above code, it produces the following result:</p>
<p><code>looking around in the bedroom.
pretty small.</code></p>
<p><a href="https://campus.datacamp.com/courses/intermediate-python/logic-control-flow-and-filtering?ex=13">Try it for yourself</a>.</p>
<p>To learn more about elif statements in Python, please see this video from our course, <a href="https://campus.datacamp.com/courses/intermediate-python/logic-control-flow-and-filtering?ex=9">Intermediate Python</a>.</p>
<iframe width="560" height="315" src="https://www.youtube.com/embed/fxszBuW3V-o" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

<p>This content is taken from DataCamp’s <a href="https://learn.datacamp.com/courses/intermediate-python-for-data-science">Intermediate Python</a> course by Hugo Bowne-Anderson.</p>


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(Tutorial) if…elif…else in Python

if…elif…else in Python

<p>The while loop is somewhat similar to an <code>if</code> statement, it executes the code inside, if the condition is True. However, as opposed to the <code>if</code> statement, the while loop continues to execute the code repeatedly as long as the condition is True.</p>
<h2 id="the-while-loop">The while Loop</h2>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594833351/while_loop1_lojtwf.png" /></center>

<p>The syntax of the while loop is very similar to the if statement, as you can see above. The while loop is not very common, but in some cases, it can be very useful.</p>
<h3 id="example-of-basic-while-loop">Example of Basic While Loop</h3>
<p>Suppose you are numerically calculating a model based on your data. This will typically involve taking the same steps repeatedly until the error between your model and your data is below some boundary. When you can reformulate the problem as <code>repeating an action until a condition is met</code>, a while loop is often the way to go.</p>
<p>In the below example, you initially start with an error equal to <code>50.0</code>. Next, you will write a while loop, in the condition part, we write error &gt; 1, so that the while loop executes again as long as the error is above 1. Inside the while loop, you divide the error by four and update the error variable. When we run it the first time, we receive 12.5.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1595459974/Screen_Shot_2020-07-22_at_7.09.27_PM_mefijo.png" /></center><br>

<p>Python will then go back to the condition of the while loop with the new error equal to 12.5. The condition will again be true, and the code is executed.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1595459974/Screen_Shot_2020-07-22_at_7.09.40_PM_ynte8e.png" /></center><br>

<p>Python will again move back to the condition of the while loop and attempt to re-run the code. Because 3.125 is greater than 1, the code makes the calculation.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1595460336/Screen_Shot_2020-07-22_at_7.25.12_PM_huvazd.png" /></center><br>

<p>Finally, the new condition of the while loop is less than 1, so the code results in an error and won&#39;t run.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594833351/while_loop2_xkd470.png" /></center><br>

<p>This example will come in handy because it&#39;s time to build a <code>while</code> loop yourself! We&#39;re going to code a <code>while</code> loop that implements a very basic control system for an <a href="https://en.wikipedia.org/wiki/Inverted_pendulum">inverted pendulum</a>. If there&#39;s an offset from standing perfectly straight, the <code>while</code> loop will incrementally fix this offset.</p>
<p>Note that if your <code>while</code> loop takes too long to run, you might have made a mistake. In particular, remember to indent the contents of the <strong>loop</strong>!</p>
<h3 id="example-of-while-loop-error-continuously-running-">Example of While Loop Error (Continuously Running)</h3>
<p>Suppose you were to comment out or remove the error value&#39;s updates and rerun the script. The error won&#39;t be updated, and the condition will always be true. This will result in the while loop running forever.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1595463438/Screen_Shot_2020-07-22_at_8.11.45_PM_gcqtu5.png" /></center><br>

<p>If you were to make this mistake on your system, you would have to interrupt the Python program by pressing the Control + C keys.</p>
<h3 id="example-of-while-loop-using-a-variable-offset">Example of While Loop Using a Variable Offset</h3>
<p>In the below example, you will create the variable <code>offset</code> with an initial value of <code>8</code>. Then you will write a <code>while</code> loop that keeps running as long as the <code>offset</code> is not equal to <code>0</code>.</p>
<p>Inside the <code>while</code> loop:</p>
<ul>
<li>You will print out the sentence <code>&quot;correcting...&quot;</code>.</li>
<li>Next, decrease the value of <code>offset</code> by 1. You can do this with <code>offset = offset - 1</code>.</li>
<li>Finally, within your while loop, print out <code>offset</code> so you can see how it changes.</li>
</ul>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594833351/while_loop_fq1f6i.png" /></center>

<p>When we run the above program, it produces the following result:</p>
<pre><code>correcting...
7
correcting...
6
correcting...
5
correcting...
4
correcting...
3
correcting...
2
correcting...
1
correcting...
0
</code></pre><p><a href="https://campus.datacamp.com/courses/intermediate-python/loops?ex=3">Try it for yourself</a>.</p>
<p>To learn more about while loops, please see this video from our course <a href="https://campus.datacamp.com/courses/intermediate-python/loops?ex=1">Intermediate Python</a>.</p>
<iframe width="560" height="315" src="https://www.youtube.com/embed/-V-F-S9v__c" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

<p>This content is taken from DataCamp’s <a href="https://learn.datacamp.com/courses/intermediate-python-for-data-science">Intermediate Python</a> course by Hugo Bowne-Anderson.</p>


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(Tutorial) Python While Loops

Python While Loops

<p>Python string method <code>split()</code> inputs a string value and outputs a list of words contained within the string by separating or splitting the words on all the whitespaces by default.  It also has an optional argument for limiting the number of splits.</p>
<p>The <code>split()</code> method converts the string into other data types like <code>lists</code> by breaking a string into pieces. Python provides us with two methods: <code>.split()</code> and <code>.rsplit()</code>.</p>
<p>Both <code>.split()</code>, and <code>.rsplit()</code> take a separating element by which we are splitting the string, and a maxsplit tells us the maximum number of substrings we want.</p>
<h3 id="example-of-using-the-split-method">Example of Using the .split() Method</h3>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594832391/split1_oz0ctj.png" /></center>

<p>Let&#39;s split the above string using the <code>.split()</code> method. Notice that the <code>.split()</code> method starts splitting at the <strong>left</strong> of the string. It takes two arguments: separator <code>sep</code> and maximum splits of the string <code>maxsplit</code>.  </p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594832391/split2_s0fk6w.png" /></center>


<h3 id="example-of-splitting-strings-into-many-substrings">Example of Splitting Strings Into Many Substrings</h3>
<p>In the below example, you will split the string <code>file</code> into many substrings at line boundaries. Then, you will print out the resulting variable <code>file_split</code>. Finally, complete the for-loop to split the strings into many substrings using commas as a separator element.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594832391/split4_qeekiv.png" /></center>

<p>When we run the above code, it produces the following result:</p>
<p><code>[&#39;mtv films election, a high school comedy, is a current example&#39;, &#39;from there, director steven spielberg wastes no time, taking us into the water on a midnight swim&#39;]
[&#39;mtv films election&#39;, &#39; a high school comedy&#39;, &#39; is a current example&#39;]
[&#39;from there&#39;, &#39; director steven spielberg wastes no time&#39;, &#39; taking us into the water on a midnight swim&#39;]</code>.</p>
<p><a href="https://campus.datacamp.com/courses/regular-expressions-in-python/basic-concepts-of-string-manipulation?ex=8">Try it for yourself</a>.</p>
<p>To learn more about string operations, please see this video from our course, <a href="https://campus.datacamp.com/courses/regular-expressions-in-python/basic-concepts-of-string-manipulation?ex=5">Regular Expressions in Python</a>.</p>
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<p>This content is taken from DataCamp’s <a href="https://learn.datacamp.com/courses/regular-expressions-in-python">Regular Expressions in Python</a> course by Maria Eugenia Inzaugarat.</p>


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Learn how you can perform various operations on string using built-in Python functions like split, join and regular expressions, and also convert them to other data types like lists.

(Tutorial) String Split in Python

String Split in Python

<p>Tuples are made of several items, just like a list, but they cannot be modified in any way. They are widely used internally in many of the systems we depend on, like databases. Tuples hold data in the order we supply it, and we can access the elements inside a tuple with an index.</p>
<p>For example, if you have a tuple like <code>(&#39;chocolate chip cookies&#39;, 15)</code> and you want to access each part of the data, you can use an index just like a list. Tuples are easier to process and more memory efficient than lists.</p>
<p>They are immutable, which means we cannot add or remove elements from them. This property of tuple is important because we can use them to ensure that our data is not altered. We can create tuples by pairing up elements.</p>
<h2 id="zipping">Zipping</h2>
<p>Often, we will have lists where we want to match up elements into pairs, and the zip function enables us to do that. Tuples are commonly created by zipping lists together with <code>zip()</code>.</p>
<h3 id="example">Example</h3>
<p>Here we have a list of most popular cookies in the US and India, and we want to build a list of pairs by the popularity rank of the cookie in each country, and we will pass them to the zip function. Then we print the result of the <code>zip</code>, and you get what looks like a list of Tuples.</p>
<p>We have two lists: <code>us_cookies</code>, <code>in_cookies</code>.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594824817/tuple2_tsbt05.png" /></center>

<p>Notice that the tuples use parenthesis as their object representation.</p>
<h2 id="unpacking">Unpacking</h2>
<p>Tuple unpacking, also sometimes called tuple expansion, allows us to assign the elements of a tuple to named variables for later use. Unpacking tuples is a very expressive way of working with data.</p>
<h3 id="example">Example</h3>
<p>The below syntax allows you to create a more readable and less error-prone code. Here we have a tuple containing top-ranked cookie from two countries, and we want to store them as <code>us_num_1</code> and <code>in_num_1</code> so that we can print them name by name.</p>
<p>We start by putting both variables as the target of the assignment statement separated by a comma. Then assign the first tuple in our <code>top_pairs</code> list to them.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594824817/tuple3_tytwea.png" /></center>


<h3 id="example">Example</h3>
<p>Here we build a <code>for</code> loop that uses tuple unpacking when iterating over the <code>top_pairs</code> list. It splits each tuple in the list into its Indian and US cookie elements. We then use each of these variables to print the cookies in order.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594824817/tuple4_hoq643.png" /></center>


<h2 id="enumerating-positions">Enumerating Positions</h2>
<p>Another useful tuple creation method is the <code>enumerate()</code> function. Enumeration is used in loops to return the position and the data in that position while looping.</p>
<h3 id="example">Example</h3>
<p>Here we enumerate our top pairs list and split that resulting tuple into index <code>idx</code> and <code>item</code>.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594824817/tuple5_spx8qm.png" /></center>


<p>To learn more about tuples in Python, please see this video from our course <a href="https://campus.datacamp.com/courses/data-types-for-data-science-in-python/fundamental-data-types?ex=4">Data Types for Data Science in Python</a>.</p>
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<p>This content is taken from DataCamp’s <a href="https://learn.datacamp.com/courses/data-types-for-data-science-in-python">Data Types for Data Science in Python</a> course by Jason Myers.</p>


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Learn to use and unpack Tuples in Python.

(Tutorial) Tuples in Python

Tuples in Python

<p>Sometimes you will want to replace occurrences of a substring with a new string, and Python has a built-in method <code>.replace()</code> to achieve it.</p>
<p>Python provides you with the <code>.replace()</code> string method that returns a copy of the string with all the occurrences of old substring replaced with the new substring given as a parameter.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594823502/regular_find9_eijuac.png" /></center>

<h2 id="arguments">Arguments</h2>
<p>It takes three arguments: the substring to replace, the new string to replace it, and an optional number that indicates how many occurrences to replace.</p>
<ul>
<li><p>old − This is the old substring to be replaced.</p>
</li>
<li><p>new − This is the new substring, which would replace the old substring.</p>
</li>
<li><p>count − If this optional argument count is given, only the first count occurrences are replaced.</p>
</li>
</ul>
<h3 id="example">Example of String Replace</h3>
<p>In the example code below, you will replace the substring house with car. The method will return a copy with all the house substrings replaced.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594823503/regular_find11_kbonez.png" /></center>

<h3 id="example">Example of String Replace with the Count Optional Argument</h3>
<p>In this second example, you specify that you only want two of the occurrences to be replaced. In the below output, you can see that the method returns the string&#39;s copy with the first two occurrences of house replaced by car.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594823502/regular_find12_qkymgr.png" /></center>

<h3 id="example">Example</h3>
<p>Here you will replace the substring <code>isn&#39;t</code> for the word <code>is</code>. Then, replace the substring <code>important</code> for the word <code>insignificant</code>, and finally, print out the result contained in the variable <code>movies_antonym</code>.</p>
<center><img src="https://res.cloudinary.com/dyd911kmh/image/upload/f_auto,q_auto:best/v1594823502/regular_find13_i2k0j9.png" /></center>

<p>When we run the above code, it produces the following result:</p>
<p><code>the rest of the story is insignificant because all it does is serve as a mere backdrop for the two stars to share the screen .</code></p>
<p><a href="https://campus.datacamp.com/courses/regular-expressions-in-python/basic-concepts-of-string-manipulation?ex=12">Try it for yourself</a>.</p>
<p>To learn more about Python String Replace, please see this video from our course, <a href="https://campus.datacamp.com/courses/regular-expressions-in-python/basic-concepts-of-string-manipulation?ex=9">Regular Expressions in Python</a>.</p>
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<p>This content is taken from DataCamp’s <a href="https://learn.datacamp.com/courses/regular-expressions-in-python">Regular Expressions in Python</a> course by Maria Eugenia Inzaugarat.</p>


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Learn to find and replace strings using regular expressions in Python.

(Tutorial) Python String Replace

Python String Replace

<p>You can add elements to a list using the append method. The <code>append()</code> method adds a single element towards the end of a list.</p>
<h3 id="example-of-the-append-method">Example of the append() method</h3>
<p>For example, let’s extend the string by adding “April” to the list with the method <code>append()</code>. Using <code>append()</code> will increase the length of the list by 1.</p>
<p><code>list.append()</code> adds a single element to a list</p>
<pre><code class="lang-python">months = [&#39;January&#39;, &#39;February&#39;, &#39;March&#39;]
months.append(&#39;April&#39;)
print(months)
</code></pre>
<pre><code>[&#39;January&#39;, &#39;February&#39;, &#39;March&#39;, &#39;April&#39;]
</code></pre><h2 id="using-list-methods-to-add-data-append-vs-extend-">Using list methods to add data: <code>append()</code> vs. <code>extend()</code></h2>
<p>The <code>.append()</code> method increases the length of the list by one, so if you want to add only one element to the list, you can use this method.</p>
<pre><code class="lang-python">x = [1, 2, 3]
x.append(4)
x
</code></pre>
<pre><code>[1, 2, 3, 4]
</code></pre><p>The <code>.extend()</code> method increases the length of the list by the number of elements that are provided to the method, so if you want to add multiple elements to the list, you can use this method.</p>
<pre><code class="lang-python">x = [1, 2, 3]
x.extend([4, 5])
x
</code></pre>
<pre><code>[1, 2, 3, 4, 5]
</code></pre><h2 id="interactive-example-of-the-append-and-extend-methods">Interactive example of the <code>append()</code> and <code>extend()</code> methods</h2>
<p>We start with the list <code>names</code>:</p>
<pre><code>names =  [&#39;Apple Inc&#39;, &#39;Coca-Cola&#39;, &#39;Walmart&#39;]
</code></pre><pre><code class="lang-python"># Append a name to the list names
names.append(&#39;Amazon.com&#39;)
print(names)
</code></pre>
<p>When we run the above code, it produces the following result:</p>
<pre><code>names =  [&#39;Apple Inc&#39;, &#39;Coca-Cola&#39;, &#39;Walmart&#39;, &#39;Amazon.com&#39;]
</code></pre><p>We can then add two additional elements to the list <code>names</code> using <code>extend()</code> and the <code>more_elements</code> list.</p>
<pre><code class="lang-python"># Extend list names
more_elements = [&#39;DowDuPont&#39;, &#39;Alphabet Inc&#39;]
names.extend(more_elements)
print(names)
</code></pre>
<p>When we run the above code, it produces the following result:</p>
<pre><code>[&#39;Apple Inc&#39;, &#39;Coca-Cola&#39;, &#39;Walmart&#39;, &#39;Amazon.com&#39;, &#39;DowDuPont&#39;, &#39;Alphabet Inc&#39;]
</code></pre><p><a href="https://campus.datacamp.com/courses/introduction-to-python-for-finance/lists-2?ex=10">Try it for yourself</a>.</p>
<p>To learn more about list methods and functions, please see this video from our course <a href="https://campus.datacamp.com/courses/introduction-to-python-for-finance/lists-2?ex=8">Introduction to Python for Finance</a>.</p>
<iframe width="560" height="315" src="https://www.youtube.com/embed/lnTq2kjUzhw?start=66" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

<p>This content is taken from DataCamp’s <a href="https://www.datacamp.com/courses/introduction-to-python-for-finance">Introduction to Python for Finance</a> course by Adina Howe.</p>


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 Learn how to use the .append() and .extend() methods to add elements to a list.

(Tutorial) Python .append() and .extend() Methods

Python .append() and .extend() Methods

<p>Object-Oriented Programming(OOP) is a  programming paradigm in where different methods are used to design software around data or objects rather than using functions. A method is just a function, talked about in the OOP context. It is object-oriented because all the processing revolves around the objects and fields. Every object has different attributes and behavior.</p>
<p>In Object-Oriented programming, the whole program can be divided into different classes to quickly understand the program execution. R is a functional programming language, and OOP will help manage large system problems. OOP used to manage GUI applications, most likely web-applications. Object-Oriented Programming is good for building tools for data analysis but bad for data analysis itself.</p>
<h3 id="systems-of-oop">Systems of OOP</h3>
<p>There are mainly two major systems of OOP, which are described below:</p>
<ul>
<li><strong>S3 Classes:</strong> These let you overload the functions.</li>
<li><strong>S4 Classes:</strong> These let you limit the data as it is quite difficult to debug the program</li>
</ul>
<p><strong>Note:</strong> These classes will be discussed in detail in the later section.</p>
<h2 id="objects-in-r">Objects in R</h2>
<p>Objects are the instance of the class. Also, everything in R is an object
and to know more look at <a href="https://www.datacamp.com/community/tutorials/data-types-in-r">Data types in R.</a>
They also can have their attributes like class, attributes,dimnnames, names, etc.</p>
<p>For example, objects are assigned a value using <code>&lt;-,</code> consider the following piece of code where &#39;a1&#39; and &#39;a2&#39; are the variables where the numeric value is assigned to it.</p>
<pre><code class="lang-python">a1 &lt;- 10
a2 &lt;- 20
</code></pre>
<p>An object can be assigned a set of numbers where &#39;a3&#39; is the object containing a vector of different numbers.</p>
<pre><code class="lang-python">a3 &lt;- c(10,20,30)
</code></pre>
<p>Here <strong>c</strong> contains the numbers,10, 20, 30 into a vector.</p>
<p>Let&#39;s take a real-life example like a student, which has attributes of name, age, class, and gender, the teacher, has a name, age, and gender.</p>
<pre><code class="lang-python">st_name &lt;- &quot;andrew&quot;
st_age &lt;- 16
st_class &lt;- 10
st_gender &lt;- &quot;male&quot;

t_name &lt;- &quot;angelina&quot;
t_age &lt;- 26
t_gender &lt;- &quot;female&quot;

student &lt;- c(st_name, st_age, st_class, st_gender)
teacher &lt;- c(t_name, t_age, t_gender)


print(student)
print(teacher)
</code></pre>
<pre><code>[1] &quot;andrew&quot; &quot;16&quot;     &quot;10&quot;     &quot;male&quot;  
[1] &quot;angelina&quot; &quot;26&quot;       &quot;female&quot;  
</code></pre><p>The above code gives the following output:</p>
<pre><code>&quot;andrew&quot; &quot;16&quot; &quot;10&quot; &quot;male&quot;  
&quot;angelina&quot; &quot;26&quot;  &quot;female&quot;
</code></pre><p>In the above code, you can see the example where there are different types of objects. The &#39;student&#39; and &#39;teacher&#39; object, also called a variable, hold type &#39;character&#39; and &#39;double.&#39;</p>
<h2 id="class-in-r">Class in R</h2>
<p>Class is the blueprint that helps to create an object and contains its member variable along with the attributes.</p>
<p>As discussed earlier in the previous section, there are two classes of R, S3, and S4.</p>
<h3 id="s3-class">S3 Class</h3>
<p>These classes help in overloading functions by splitting them into generic and methods.</p>
<p>  <strong>functions = generic + methods</strong></p>
<p>S3 is very different from other programming languages like C#, Java, etc. Because it&#39;s straightforward to implement, it uses only the first argument to dispatch. That&#39;s why it doesn&#39;t require too much knowledge as a programmer&#39;s perspective.</p>
<p>S3 works by defining a strict naming convention of generic dot class.</p>
<pre><code>                             generic.class
</code></pre><p>The arguments of methods should contain arguments of generic, and method should include a <strong>...arg</strong>.</p>
<h3 id="constructing-along-with-example-of-s3-class">Constructing along with Example of S3 Class</h3>
<p>You will be demonstrated to construct an S3 class in the following example, which shows the creation of the list where components are being passed along with proper class name followed by the result to be printed.</p>
<p>The following example shows &#39;studentBio&#39; contains a list where components are passed as a list where &#39;student_name,&#39; &#39;student_age,&#39; and &#39;student_contact&#39; are being given. The class is named &#39;Student Info,&#39; and &#39;studentBio&#39; is the newly created class whose values are displayed below.</p>
<pre><code class="lang-python">studentBio &lt;- list(studentName = &quot;Harry Potter&quot;, studentAge = 19, studentContact=&quot;London&quot;)
class(studentBio) &lt;- &quot;StudentInfo&quot;
studentBio
</code></pre>
<pre><code>$studentName
[1] &quot;Harry Potter&quot;

$studentAge
[1] 19

$studentContact
[1] &quot;London&quot;

attr(,&quot;class&quot;)
[1] &quot;StudentInfo&quot;
</code></pre><p>The above code gives the output as below:</p>
<pre><code>$studentName
 &quot;Harry Potter&quot;

$studentAge
19

$studentContact
&quot;London&quot;

attr(,&quot;class&quot;)
&quot;StudentInfo&quot;
</code></pre><p>If you are not comfortable about writing function in R, then read a <a href="https://www.datacamp.com/community/tutorials/functions-in-r-a-tutorial">A Tutorial on Using Functions in R!</a></p>
<h3 id="creating-your-own-generic-method-in-s3">Creating Your Own Generic Method in S3</h3>
<p>You will be implementing your generic function below by using the following code.</p>
<p>The code below shows the generic function called &#39;contact&#39; where the function passing with the object is assigned to it. Also, &#39;UseMethod&#39; is used with the generic function called &#39;contact&#39; is passed where &#39;dispatching&#39; of method occurs, which is the process where the result varies based on the arguments passed.</p>
<pre><code class="lang-python">contact &lt;- function(object) {
UseMethod(&quot;contact&quot;)
}
</code></pre>
<p>Let&#39;s make a method for the particular class that you&#39;ve created earlier named &#39;StudentInfo.&#39;
The method &#39;contact&#39; followed by dot notation along with the class &#39;StudentInfo&#39; is used where the function body contains the access of the attribute  &#39;studentContact&#39; is done by using &#39;$.&#39;</p>
<pre><code class="lang-python">contact.StudentInfo &lt;- function(object) {
cat(&quot;Your contact is&quot;, object$studentContact, &quot;\n&quot;)
}
contact(studentBio)
</code></pre>
<pre><code>Your contact is London
</code></pre><p>The above code uses <code>object$studentContact</code>, where the object passed as an argument to function along with &#39;$&#39; to access attribute &#39;studentContact,&#39; which results in output as below.</p>
<pre><code>Your contact is London
</code></pre><h2 id="s4-class">S4 Class</h2>
<p>S4 Class is stricter, conventional, and closely related to Object-Oriented concepts. The classes are represented by the formal class definitions of S4. More specifically, S4 has setter and getter functions for methods and generics. As compared to the S3 class, S4 can be able to facilitate multiple dispatches.</p>
<p>Let us see the above-discussed classes of R by creating them and discuss with an example.</p>
<p>An S4 class is defined using the set class function.</p>
<pre><code> setClass()
</code></pre><h3 id="constructing-along-with-example-of-s4-class">Constructing along with Example of S4 Class</h3>
<p>As discussed earlier, the S4 class is defined by the setClass() method. You will use the setClass() method to create and define the S4 class. We will use a subroutine to verify that the data is consistent (validation) and also set the default values (the paradigm).</p>
<p>Following is the code to define the class and its slots:</p>
<p>The following is used to define a class, also called &#39;prototype&#39;, where the slots are defined where the class name is &#39;employee&#39;, name is a character, id as a numeric, and contact as a character.</p>
<pre><code class="lang-python">setClass(&quot;employee&quot;, slots=list(name=&quot;character&quot;, id=&quot;numeric&quot;, contact=&quot;character&quot;))
</code></pre>
<p>The following code can create the specific instance or objects of S4.</p>
<p>Let&#39;s create an object using &#39;new&#39; with the class name inside as &#39;employee&#39; with the slots like name, id, and contact are filled with a value.</p>
<pre><code class="lang-python">obj &lt;- new(&quot;employee&quot;,name=&quot;Steven&quot;, id=1002, contact=&quot;West Avenue&quot;)
obj
</code></pre>
<pre><code>An object of class &quot;employee&quot;
Slot &quot;name&quot;:
[1] &quot;Steven&quot;

Slot &quot;id&quot;:
[1] 1002

Slot &quot;contact&quot;:
[1] &quot;West Avenue&quot;
</code></pre><pre><code>An object of class &quot;employee&quot;
Slot &quot;name&quot;:
&quot;Steven&quot;

Slot &quot;id&quot;:
1002

Slot &quot;contact&quot;:
&quot;West Avenue&quot;
</code></pre><p>The above output shows that the object created was of class &quot;employee&quot; and the Slot with &quot;name&quot; called &quot;Steven&quot; along with Slot &quot;id&quot; with value 1002 and Slot &quot;contact&quot; with value is &quot;West Avenue&quot;.</p>
<h3 id="function-and-commands">Function and commands</h3>
<p>For checking whether an object is an S4 object or not following two commands can be used:</p>
<p>The command &#39;is.object(obj)&#39;checks whether a variable or instance refers to an object or not.</p>
<pre><code class="lang-python">is.object(obj)
</code></pre>
<p>TRUE</p>
<p>The above code gives the following output as below:</p>
<pre><code>TRUE
</code></pre><p>The command &#39;is.S4(obj)&#39;checks, whether a variable or instance is an S4 object or not.</p>
<pre><code class="lang-python">isS4(obj)
</code></pre>
<p>TRUE</p>
<p>The above code gives the following output as below:</p>
<pre><code>TRUE
</code></pre><h3 id="accessing-and-modifying-the-slot-value">Accessing and Modifying the slot value</h3>
<h4 id="accessing-the-slot">Accessing the slot</h4>
<p>The slot can be accessed using the &quot;@&quot; instead of &quot;$&quot;.</p>
<p>&#39;obj@name&#39; is used where the object name along with the slot name is to access the name &#39;Steven&#39; and is similarly done to &#39;obj@id&#39;.</p>
<pre><code class="lang-python">obj@name
obj@id
</code></pre>
<p>&#39;Steven&#39;</p>
<p>1002</p>
<p>The above code gives the following output:</p>
<pre><code>&#39;Steven&#39;
1002
</code></pre><h4 id="modifying-the-slot">Modifying the slot</h4>
<p>Let&#39;s modify the slot value just by using the assignment operator(&quot;&lt;-&quot;) where the &#39;obj@contact&#39; is assigned with a new value as &quot;North Avenue&quot;.</p>
<pre><code class="lang-python">obj@contact &lt;- &quot;North Avenue&quot;
obj
</code></pre>
<pre><code>An object of class &quot;employee&quot;
Slot &quot;name&quot;:
[1] &quot;Steven&quot;

Slot &quot;id&quot;:
[1] 1002

Slot &quot;contact&quot;:
[1] &quot;North Avenue&quot;
</code></pre><p>The above code gives the following output:</p>
<pre><code>An object of class &quot;employee&quot;
Slot &quot;name&quot;:
&quot;Steven&quot;

Slot &quot;id&quot;:
1002

Slot &quot;contact&quot;:
&quot;North Avenue&quot;
</code></pre><p>The above output shows that the Slot &quot;contact&quot; has changed it&#39;s value previously &quot;West Avenue&quot; to &quot;North Avenue&quot;.</p>
<p>Alternatively, there is an option to use &#39;slot()&#39; to change the value.</p>
<p>&#39;slot(obj, &quot;id&quot;)&#39; indicates the slot &quot;id&quot; value to ve changed with the assignment of 1004, and the result is printed with &#39;obj&#39;.</p>
<pre><code class="lang-python">slot(obj,&quot;id&quot;) &lt;- 1004
obj
</code></pre>
<pre><code>An object of class &quot;employee&quot;
Slot &quot;name&quot;:
[1] &quot;Steven&quot;

Slot &quot;id&quot;:
[1] 1004

Slot &quot;contact&quot;:
[1] &quot;North Avenue&quot;
</code></pre><pre><code>An object of class &quot;employee&quot;
Slot &quot;name&quot;:
&quot;Steven&quot;

Slot &quot;id&quot;:
1004

Slot &quot;contact&quot;:
&quot;North Avenue&quot;
</code></pre><p>The above output shows that the Slot &quot;id&quot; has changed its value previously 1002 to 1004.</p>
<h3 id="creating-your-own-generic-method-in-s4">Creating Your Own Generic Method in S4</h3>
<p>Let&#39;s create a function that helps print the output according to our needs, where the &#39;setMethod()&#39; and the generic function called &#39;show()&#39; is used. Also, all the slots&#39; value is accessed by &#39;@&#39;, and their names are printed out. Finally, the output is obtained with the help of &#39;obj&#39;.</p>
<pre><code class="lang-python">setMethod(&quot;show&quot;,
&quot;employee&quot;,
function(object) {
cat(&quot;Name:&quot;,object@name, &quot;\n&quot;)
cat(&quot;Id:&quot;,object@id, &quot;\n&quot;)
cat(&quot;Contact:&quot;, object@contact, &quot;\n&quot;)
}
)
obj
</code></pre>
<pre><code>Name: Steven
Id: 1004
Contact: North Avenue
</code></pre><pre><code>Name: Steven
Id: 1004
Contact: North Avenue
</code></pre><p>The above output shows that the results are printed as in the form of Slot names along with respective Slot values.</p>
<h3 id="congratulations">Congratulations</h3>
<p>Congratulations, you have made it to the end of this tutorial!</p>
<p>In this tutorial, you&#39;ve learned about Object-Oriented Programming(OOP) along with R&#39;s objects, different classes like S3 and S4, along with its construction, creating its generic function with examples and many more.</p>
<p>If you would like to learn more about R, take DataCamp&#39;s <a href="https://www.datacamp.com/courses/object-oriented-programming-in-r-s3-and-r6">Object-Oriented Programming with S3 and R6 in R</a>.</p>


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<center>
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<p>The factors are the variable in R, which takes the categorical variable and stores data in levels. The primary use of this function can be seen in data analysis and specifically in statistical analysis. Also, it helps to reduce data redundancy and to save a lot of space in the memory.</p>
<p><b>Note: A categorical variable is those variables that take values based on the labels or names. For example, the blood type of a human can be A, B, AB, or O.</b></p>
<h3 id="factor-function">factor function</h3>
<p><b>Usage:</b> Categorize the data which have less number of values.<br>
<b>Parameters:factor(v):</b>v can be vector of values.</p>
<p>Let&#39;s see the example of a factor in action.<br></p>
<p>You can see below code where there are two categorical variables, namely &quot;Male&quot; and &quot;Female&quot;, also called factor values.</p>
<pre><code class="lang-python">gender &lt;- c(&quot;Male&quot;,&quot;Female&quot;,&quot;Female&quot;,&quot;Male&quot;,&quot;Female&quot;)
</code></pre>
<p>Let&#39;s create a factor for the gender where &#39;factor(gender)&#39; is used and saved to a variable called &#39;gender.factor&#39;.</p>
<pre><code class="lang-python">gender.factor &lt;- factor(gender)
gender.factor
</code></pre>
<ol class=list-inline>
    <li>Male</li>
    <li>Female</li>
    <li>Female</li>
    <li>Male</li>
    <li>Female</li>
</ol>

<details>
    <summary style=display:list-item;cursor:pointer>
        <strong>Levels</strong>:
    </summary>
    <ol class=list-inline>
        <li>&#39;Female&#39;</li>
        <li>&#39;Male&#39;</li>
    </ol>
</details>


<p>The above code gives the output as below:</p>
<pre><code>Male Female Female Male Female
Levels:
&#39;Female&#39; &#39;Male&#39;
</code></pre><p>You can see above where values are printed the same as the input vector. Additionally, &#39;Levels&#39;, which are &#39;Female&#39; and &#39;Male&#39; are sorted alphabetically.</p>
<h3 id="structure-of-factor-function">Structure of factor function</h3>
<p>Let&#39;s examine the structure for factor function by using &#39;str(gender.factor)&#39; in the code below.</p>
<pre><code class="lang-python">str(gender.factor)
</code></pre>
<pre><code> Factor w/ 2 levels &quot;Female&quot;,&quot;Male&quot;: 2 1 1 2 1
</code></pre><pre><code>Factor w/ 2 levels &quot;Female&quot;,&quot;Male&quot;: 2 1 1 2 1
</code></pre><p>The above output shows that there is a factor of 2 levels. factor converts the character vector as gender into a vector of integer values. &quot;Female&quot; is the first level encoded as 1 whereas the &quot;Male&quot; is the second level, encoded as 2.</p>
<p>Also, the primary purpose of encoding from character to numeric is that the categories can belong, repeating is redundant, which can take a lot of space in the memory. But, using factor reduces all the burden to save up space in the memory.</p>
<h3 id="changing-order-levels">Changing Order Levels</h3>
<p>Let&#39;s change the order levels, so the levels of &quot;Female&quot; will become 2 and &quot;Male&quot; as 1.</p>
<p>Let&#39;s make a new factor for the gender by changing the levels of &quot;Male&quot; and &quot;Female&#39; by passing it as a vector input to the &quot;levels&quot;. Finally, the resultant output is saved to the variable named &quot;gender.factor2&#39;.</p>
<pre><code class="lang-python">gender.factor2 &lt;- factor(gender,levels=c(&quot;Male&quot;,&quot;Female&quot;))
gender.factor2
str(gender.factor2)
</code></pre>
<ol class=list-inline>
    <li>Male</li>
    <li>Female</li>
    <li>Female</li>
    <li>Male</li>
    <li>Female</li>
</ol>

<details>
    <summary style=display:list-item;cursor:pointer>
        <strong>Levels</strong>:
    </summary>
    <ol class=list-inline>
        <li>&#39;Male&#39;</li>
        <li>&#39;Female&#39;</li>
    </ol>
</details>


<pre><code> Factor w/ 2 levels &quot;Male&quot;,&quot;Female&quot;: 1 2 2 1 2
</code></pre><p>The &#39;gender.factor2&#39; is printed along with it&#39;s structure printed using &#39;str(gender.factor2)&#39; where the following changes can be seen.</p>
<pre><code>Male Female Female Male Female
 Levels:
&#39;Male&#39; &#39;Female&#39;
 Factor w/ 2 levels &quot;Male&quot;,&quot;Female&quot;: 1 2 2 1 2
</code></pre><p>The above code gives the output where the encoding of &quot;Male&quot; is 1, and &quot;Female&quot; is 2. It&#39;s different from &#39;gender.factor&#39;, which was opposite in the above code.</p>
<h3 id="renaming-a-factor-levels">Renaming a Factor levels</h3>
<p>Let&#39;s change the name of the vector values in the input by specifying the regular use of &#39;levels&#39;  as the first argument with values &quot;Male&quot; and &quot;Female&quot; and the expected changed vector values using &#39;labels&#39; as the second argument with &quot;Gen_Male&quot; and &quot;Gen_Female&quot; respectively.</p>
<pre><code class="lang-python">factor(gender,levels = c(&quot;Male&quot;,&quot;Female&quot;),labels = c(&quot;Gen_Male&quot;,&quot;Gen_Female&quot;))
</code></pre>
<ol class=list-inline>
    <li>Gen_Male</li>
    <li>Gen_Female</li>
    <li>Gen_Female</li>
    <li>Gen_Male</li>
    <li>Gen_Female</li>
</ol>

<details>
    <summary style=display:list-item;cursor:pointer>
        <strong>Levels</strong>:
    </summary>
    <ol class=list-inline>
        <li>&#39;Gen_Male&#39;</li>
        <li>&#39;Gen_Female&#39;</li>
    </ol>
</details>


<pre><code>Gen_Male Gen_Female Gen_Female Gen_Male Gen_Female
 Levels:
&#39;Gen_Male&#39; &#39;Gen_Female&#39;
</code></pre><p>The above code gives the output where the name is changed for &quot;Male&quot; to &quot;Gen_Male&quot; and &quot;Female&quot; to &quot;Gen_Female&quot;.</p>
<h3 id="ordering-a-categorical-variable">Ordering a Categorical Variable</h3>
<p>Let&#39;s look at a different example when dealing with ordinal categorical values where ordered matters. For instance, for the size of a pant, there might be a size which is considered as Large as &quot;L&quot;, Extra Large as &quot;XL&quot; and Extra extra Large as &quot;XXL&quot; is arranged in ascending order.
The code below contains the collection of vector input of characters &quot;L&quot;, &quot;XL&quot; and &quot;XXL&quot; and stored to &#39;pant&#39;.
&#39;pant.factor&#39; is the variable which has parameter containing levels arranged in ascending order as &#39;levels = c(&quot;L&quot;, &quot;XL&quot;, &quot;XXL&quot;)&#39; and finally &#39;ordered = TRUE&#39;, which makes the sorting possible according to your need.</p>
<pre><code class="lang-python">pant &lt;- c(&quot;XL&quot;,&quot;L&quot;,&quot;XL&quot;,&quot;XXL&quot;,&quot;L&quot;,&quot;XL&quot;)
pant.factor &lt;- factor(pant,ordered = TRUE,levels = c(&quot;L&quot;,&quot;XL&quot;,&quot;XXL&quot;))
pant.factor
pant.factor[1] &gt; pant.factor[2]
</code></pre>
<ol class=list-inline>
    <li>XL</li>
    <li>L</li>
    <li>XL</li>
    <li>XXL</li>
    <li>L</li>
    <li>XL</li>
</ol>

<details>
    <summary style=display:list-item;cursor:pointer>
        <strong>Levels</strong>:
    </summary>
    <ol class=list-inline>
        <li>&#39;L&#39;</li>
        <li>&#39;XL&#39;</li>
        <li>&#39;XXL&#39;</li>
    </ol>
</details>



<p>TRUE</p>
<pre><code>XL L XL XXL L XL
 Levels:&#39;L&#39;&lt; &#39;XL&#39; &lt; &#39;XXL&#39;
TRUE
</code></pre><p>The above output shows the normal output at first where all the vector values (XL, L, XL, XXL, L, XL) are printed out by using &#39;pant.factor&#39;. The levels of vector values &#39;L&#39; &lt; &#39;XL&#39; &lt; &#39;XXL&#39; are arranged in the ascending order, which is printed at the console. Also, &#39;pant.factor[1] &gt; pant.factor[2]&#39; compares whether &quot;XL&quot; is greater than &quot;L&quot;, which results in TRUE being printed.</p>
<h2 id="congratulations">Congratulations</h2>
<p>Congratulations, you have made it to the end of this tutorial!</p>
<p>In this tutorial, you have covered the factor function in R, along with an example, and its structure, order levels, renaming of the levels, and finally, with the ordering of categorical values.</p>
<p>If you would like to learn more about R, take DataCamp&#39;s <a href="https://www.datacamp.com/learn/r-programming/">Introduction to R course.</a></p>


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<p>The &#39;ifelse()&#39; function is the alternative and shorthand form of the R if-else statement. Also, it uses the &#39;vectorized&#39; technique, which makes the operation faster. All of the vector values are taken as an argument at once rather than taking individual values as an argument multiple times.</p>
<h3 id="syntax">Syntax</h3>
<p>The syntax of &#39;ifelse()&#39; function in R is done by:<br>
<b>ifelse(logical_expression, a , b)</b><br></p>
<p>The argument above in &#39;ifelse&#39; states that:<br>
    1.<b>logical_expression:</b> Indicates an input vector, which in turn will return the vector of the same size as output.<br>
    2.<b> a:</b> Executes when the logical_expression is TRUE.<br>
    3.<b> b:</b> Executes when the logical_expression is FALSE.</p>
<h3 id="example-odd-or-even-">Example (Odd or Even)</h3>
<p>Let&#39;s quickly look at an example below where the following code will check whether numbers are odd or even.
&#39;v&#39; is the vector which consists of a list of numbers. In &#39;ifelse&#39; function the expression &#39;v%%2==1&#39; checks the remainder of each number in the &#39;v&#39; to be one and happens to be TRUE will print &quot;odd&quot; otherwise in FALSE will print &quot;even&quot;.</p>
<pre><code class="lang-python">v = c(14,7,6,9,2)
ifelse(v %% 2 == 1,&quot;odd&quot;,&quot;even&quot;)
</code></pre>
<ol class=list-inline>
    <li>&#39;even&#39;</li>
    <li>&#39;odd&#39;</li>
    <li>&#39;even&#39;</li>
    <li>&#39;odd&#39;</li>
    <li>&#39;even&#39;</li>
</ol>



<p>The above code gives the output as:<br>
<b>&#39;even&#39; &#39;odd&#39; &#39;even&#39; &#39;odd&#39; &#39;even&#39;</b><br>
The internal working of code above produces a logical vector as c(FALSE,TRUE,FALSE,TRUE,FALSE). The first parameter will form a string vector of c(&quot;odd&quot;,&quot;odd&quot;,&quot;odd&quot;,&quot;odd&quot;,&quot;odd&quot;) also the second parameter which in turn will produce string vector as c(&quot;even&#39;,&quot;even&quot;,&quot;even&quot;,&quot;even&quot;,&quot;even&quot;). Finally when the individual vector elements is TRUE gets change to &#39;odd&#39; whereas the &#39;FALSE&#39; will change to &#39;even&#39;.</p>
<h3 id="example-pass-or-fail-">Example(Pass or Fail)</h3>
<p>The example below demonstrates the use of &#39;ifelse()&#39; function along with the use of a DataFrame. If Student scores marks above 40, then he/she may be considered &#39;Pass&#39; otherwise considered &#39;Fail&#39; in an exam.</p>
<p>Let&#39;s quickly create a Data Frame where there is a name of a student as &quot;Student&quot; column with vector as input containing (&quot;Ron&quot;, &quot;Jake&quot;, &quot;Ava&quot;, &quot;Sophia&quot;, &quot;Mia&quot;). Another column is &quot;Marks&quot;, which contains a vector input with the value as (35,75,45,30,85). Finally, both columns are combined to form data frames and store to &#39;x&#39;.</p>
<pre><code class="lang-python">x &lt;- data.frame(&quot;Student&quot; = c(&quot;Ron&quot;,&quot;Jake&quot;,&quot;Ava&quot;,&quot;Sophia&quot;,&quot;Mia&quot;),&quot;Marks&quot; = c(35,75,45,30,85))
str(x)
</code></pre>
<pre><code>&#39;data.frame&#39;:    5 obs. of  2 variables:
 $ Student: Factor w/ 5 levels &quot;Ava&quot;,&quot;Jake&quot;,&quot;Mia&quot;,..: 4 2 1 5 3
 $ Marks  : num  35 75 45 30 85
</code></pre><pre><code>&#39;data.frame&#39;:    5 obs. of  2 variables:
 $ Student: Factor w/ 5 levels &quot;Ava&quot;,&quot;Jake&quot;,&quot;Mia&quot;,..: 4 2 1 5 3
 $ Marks  : num  35 75 45 30 85
</code></pre><p>The above code shows the structure of a Data Frame using the &#39;str(x)&#39; where it says there are 5 observations with 2 variables with the respective values of Student and Marks printed out.</p>
<pre><code class="lang-python">x$Result = ifelse(x$&quot;Marks&quot;&gt;40,&quot;Pass&quot;,&quot;Fail&quot;)
print(x)
</code></pre>
<p>The above code gives the output as below:</p>
<pre><code>    Student Marks Result
1    Ron    35   Fail
2   Jake    75   Pass
3    Ava    45   Pass
4 Sophia    30   Fail
5    Mia    85   Pass
</code></pre><p>The above code has <code>&#39;x$Result&#39;</code> as a variable is used to add a new column &#39;Result&#39; in a Data Frame. The &#39;ifelse()&#39; function has an expression as <code>&#39;x$&quot;Marks&quot;&gt;40&#39;</code>, which checks the vector values from Marks and decides the &#39;Result&#39; to be &#39;Pass&#39; when Marks is greater than 40 otherwise the &#39;Result&#39; is &#39;Fail&#39;.</p>
<h2 id="congratulations">Congratulations</h2>
<p>Congratulations, you have made it to the end of this tutorial!</p>
<p>You&#39;ve learned about R&#39;s ifelse() function with is syntax along with it&#39;s help in finding whether a number is Odd or Even and finally with its example to see whether a student is Pass or Fail in an exam.</p>
<p>If you would like to learn more about R, take DataCamp&#39;s <a href="https://www.datacamp.com/learn/r-programming/">Introduction to R course</a>.</p>


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