Python Data Type Conversion Tutorial

In the example, an int value a_int was added to a float value b_float, and the result was automatically converted to a float value c_sum without you having to tell the compiler. This is the implicit data conversion.

Why was the float value not converted to integer instead?

This is due to a broader concept of type promotion in computer science. Simply put, this is a defense mechanism of the compiler that allows you to perform operations whenever possible by converting your data into a different supertype without the loss of information.

That means that the conversion from float to integer is not done because then the compiler will need to remove the fractional part leading to the loss of information.

Python Explicit Data Type Conversion

Explicit conversion, also known as type casting, is when data type conversion takes place because you clearly defined it in your program. You basically force an expression to be of a specific type. The general form of an explicit data type conversion is as follows:

(required_data_type)(expression)

Note: as you can imagine, with explicit data type conversion, there is a risk of information loss since you're forcing an expression to be of a specific type.

With all of this in mind, you can dig into some of the commonly used explicit data type conversions...

Primitive Versus Non-Primitive Data Structures

Primitive data structures are the building blocks for data manipulation and contain pure, simple values of data. Python has four primitive variable types:

• Integers
• Float
• Strings
• Boolean

Non-primitive data structures don't just store a value but rather a collection of values in various formats. In Python, you have the following non-primitive data structures:

• Lists
• Tuples
• Dictionary
• Sets

You can learn more about them with DataCamp's Data Structures in Python Tutorial.

Primitive Data Structures Conversions

Integer and Float Conversions

Integers and floats are data types that deal with numbers.

To convert the integer to float, use the float() function in Python. Similarly, if you want to convert a float to an integer, you can use the int() function.

a_int = 3
b_int = 2

# Explicit type conversion from int to float
c_float_sum = float(a_int + b_int)
print(c_float_sum)

5.0

a_float = 3.3
b_float = 2.0

# Explicit type conversion from float to int
c_int_sum = int(a_float + b_float)
print(c_int_sum)

c_float_sum = a_float + b_float
print(c_float_sum)

5
5.3

Real to Complex Data Type Conversion

You can convert integers to complex numbers by using complex(real,imag). It requires two integers (real and imaginary numbers) and converts real numbers to complex numbers.

real = 2
imag = 5
print(complex(real, imag))

(2+5j)

Data Type Conversion with Strings

A string is a collection of one or more characters (letters, numbers, symbols). You may need to convert strings to numbers or numbers to strings fairly often. Check out how you can do this using the str() function:

price_cake = 15
price_cookie = 6
total = price_cake + price_cookie
print("The total is: " + total  + "$")

 
---------------------------------------------------------------------------

TypeError                                 Traceback (most recent call last)

<ipython-input-12-54bd76b9b4bd> in <module>()
      2 price_cookie = 6
      3 total = price_cake + price_cookie
----> 4 print("The total is: " + total  + "$")


TypeError: Can't convert 'int' object to str implicitly

The example above gives a TypeError, informing that the compiler cannot implicitly convert an integer value to a string.

It might seem intuitive to you what the program should do here. However, the compiler might not always be sure, and that's why it provides a mechanism with the explicit type casting so that you can clearly state what you want. Let's see the same example with type casting:

price_cake = 15
price_cookie = 6
total = price_cake + price_cookie
print("The total is: " + str(total)  + "$")

The total is: 21$

It works the same way when you convert float to string values.

In Python, you can also convert strings to integer and float values whenever possible. Let's see what this means:

price_cake = '15'
price_cookie = '6'

# String concatenation
total = price_cake + price_cookie
print("The total is: " + total + "$")

# Explicit type conversion to integer
total = int(price_cake) + int(price_cookie)
print("The total is: " + str(total)  + "$")

The total is: 156$
The total is: 21$

Let's break down the code.

price_cake and price_cookie are initially strings. Then, you need to find the total, which means they have to be first converted to their corresponding integer values. Else, the compiler will assume the operation that you want is a string concatenation rather than a numerical addition. You then need to put this value into the final display string and consequently need to convert the total to a string so as to concatenate it with the rest of the display message.

Hopefully, this example helps you to see the importance of data type conversions. Even though this is a very small example of data type conversion, you can already see how useful it can be.

Note: did you notice the "whenever possible" when trying to convert a string to integers or float? This is because it is not always possible to convert strings to numbers and apply numerical operations on them. The compiler is aware of this and will, therefore, give you an error when you try to do so. Check out the example below:

price_cake = 'fifteen'
price_cookie = 'six'
total = int(price_cake) + int(price_cookie)

---------------------------------------------------------------------------

ValueError                                Traceback (most recent call last)

<ipython-input-25-80591b8accda> in <module>()
      1 price_cake = 'fifteen'
      2 price_cookie = 'six'
----> 3 total = int(price_cake) + int(price_cookie)


ValueError: invalid literal for int() with base 10: 'fifteen'

Non-Primitive Data Structures

Type Conversion to Tuples and Lists

Just like with integers and floats, you can also convert lists to tuples and tuples to lists.

Remember what tuple and lists are? Lists and Tuples in Python are used to store a collection of homogeneous items. The difference between tuples and lists is that tuples are immutable, which means once defined, you cannot delete, add or edit any values inside it.

Why would you convert lists to tuples?

That's because tuples are immutable data type and allows substantial optimization to the programs that you create.

And why would you convert tuples to lists?

Maybe you want to make changes to the initial tuple. Thus, you can convert them to lists and then make the change, then convert them back to tuples.

You can use the tuple() function to return a tuple version of the value passed to it, and similarly the list() function to convert to a list:

a_tuple = ('a', 1) ,('f', 2), ('g', 3)
b_list = [1,2,3,4,5]

print(tuple(b_list))
print(list(a_tuple))

(1, 2, 3, 4, 5)
[('a', 1), ('f', 2), ('g', 3)]

You can also convert a string into a list or a tuple. 

dessert = 'Cake'

# Convert the characters in a string to individual items in a tuple
print(tuple(dessert))

# Convert a string into a list
dessert_list = list(dessert)
dessert_list.append('s')
print(dessert_list)

('C', 'a', 'k', 'e')
['C', 'a', 'k', 'e', 's']

Type Conversion to Dictionaries, and Sets

You can use the dict() function to convert a tuple to a dictionary and set() to convert a list to a set. 

print(dict(a_tuple))
print(set(b_list))

{'a': 1, 'f': 2, 'g': 3}
{1, 2, 3, 4, 5}

Simpler to other conversion functions, you just need to provide a function name to convert any datatype to dictionaries and sets. 

Unicode, Binary, Octal, and Hexadecimal Integers in Python

The number systems refer to the number of symbols or characters used to represent any numerical value. The number system that you typically use every day is called decimal. In the decimal system, you use ten different symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. With these ten symbols, you can represent any quantity. Unicode, Binary, Hexadecimal, and Octal refer to different number systems.

When you run out of symbols, you go to the next digit placement. In the decimal system, to represent one higher than 9, you use 10 meaning one unit of ten and zero units of one. However, it is different in other number systems. For example, when you consider a binary system which only uses two symbols: 0 and 1, when you run out of symbols, you need to go to the next digit placement. So this is how you will count in binary: 0, 1, 10, 11, 100, 101 and so on.

Let's check out some of the number systems in more detail in the next sections.

Convert Binary to Decimal in Python

Binary integers are the number represented with base two. Which means in the binary number system, there are only two symbols used to represent numbers: 0 and 1. When you count up from zero in binary, you run out of symbols more quickly: 0, 1, ???

Furthermore, there are no more symbols left. You do not go to the digit 2 because 2 doesn't exist in binary. Instead, you use a special combination of 1s and 0s. In a binary system, 1000 is equal to 8 in decimal. In binary, you use powers of two, which means 8 is basically: (1(2^3)) + (0(2^2)) + (0(2^1)) + (0(2^0))= 8. The position of the 1 and 0 defines the power to which 2 is to be raised to.

Let's see this with a more complex example to make it clear:

Binary Number = 1001111
Decimal value = (1*(2^6)) + (0*(2^5)) + (0*(2^4)) + (1*(2^3)) + (1*(2^2)) + (1*(2^1)) + (1*(2^0))
              = 79

In Python, you can simply use the bin() function to convert from a decimal value to its corresponding binary value.

And similarly, the int() function to convert a binary to its decimal value. The int() function takes as second argument the base of the number to be converted, which is 2 in the case of binary numbers.

a = 79

# Base 2(binary)
bin_a = bin(a)
print(bin_a)
print(int(bin_a, 2)) #Base 2(binary)

0b1001111
79

Convert Octal to Decimal in Python

Octal is another number system with fewer symbols to use than the conventional decimal number system. Octal is base eight, which means that eight symbols are used to represent all the quantities. They are 0, 1, 2, 3, 4, 5, 6, and 7. After 7 is 10, since 8 doesn't exist.

Just like you used powers of two in binary to determine the value of a number, you will use powers of 8 since this is base eight.

In a binary system, 10 is equal to 8 in octal. Let's break it down: (1(8^1)) + (0(8^0))= 8.

A more complex example:

Octal Number = 117
Decimal value = (1*(8^2)) + (1*(8^1)) + (7*(8^0))
              = 79

In Python, you can use the oct() function to convert from a decimal value to its corresponding octal value. Alternatively, you can also use the int() function along with the correct base, which is 8 for the octal number system.

a = 79

# Base 8(octal)
oct_a = oct(a)
print(oct_a)
print(int(oct_a, 8))

0o117
79

Convert Hexadecimal to Decimal in Python

Hexadecimal is a base 16 number system. Unlike binary and octal, hexadecimal has six additional symbols that it used beyond the numbers found in the decimal number system.

But what comes after 9?

Once additional symbols are needed beyond the normal numerical values, letters are to be used. So in hexadecimal, the total list of symbols used is: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F.

Using the same example as earlier:

Hexadecimal Number = 4F
Decimal value = (4*(16^1)) + (F*(16^0))
              = 79

In Python, you can use the hex() function to convert from a decimal value to its corresponding hexadecimal value, or the int() function with base 16 for the hexadecimal number system.

a = 79

# Base 16(hexadecimal)
hex_a = hex(a)
print(hex_a)
print(int(hex_a, 16))

0x4f
79

Convert Unicode to Character

Python chr() converts unicode integers to string. Unicode is a universally accepted character coding for displaying the written texts of the diverse languages.

We have provided various unicode integers to the chr() function to display “DATACAMP”. You can also use ord() to convert a single character to a unicode integer. 

print(
    chr(68),
    chr(65),
    chr(84),
    chr(65),
    chr(67),
    chr(65),
    chr(77),
    chr(80),
)

D A T A C A M P

You Made It!

Congrats! You learned about data type conversions in Python, primarily using built-in methods. This will definitely help you work around various data types, providing you with more flexibility when writing your programs.

We have an excellent course on Intermediate Python for Data Science where you can learn how to plot your data using matplotlib, and work with dictionaries and the famous pandas DataFrame. You will also see how you can control the flow of your program with loops. There is also a case study at the end of the course where you will get to apply all that you have learned and put your knowledge to work!