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if…elif…else
are conditional statements used in Python that help you to automatically execute different code based on a particular condition. This tutorial explains each statement in this Python construct, along with examples.
To easily run all the example code in this tutorial yourself, you can create a DataLab workbook for free that has Python pre-installed and contains all code samples. For more practice on if
statements, check out this hands-on DataCamp exercise.…
elif…
else
Learn Python From Scratch
if condition
The if
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.
if condition:
expression
Example of if
Suppose you have a variable z
, equal to 4. If the value is 'even', you will print z
is 'even'. You will use modulo operator 2, which will return 0 if z
is 'even'. As soon as you run the below code, Python will check if the condition holds. If True, the corresponding code will be executed.
z = 4
if z % 2 == 0: # True
print("z is even")
z is even
Example of multiple lines inside if statement
It is perfectly fine to have more lines inside the if
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.
z = 4
if z % 2 == 0:
print("checking" + str(z))
print("z is even")
checking 4
z is even
Example of a False if statement
Let's change the value of z
to be odd. You will notice that the code will not print anything since the condition will not be passed, i.e., False.
z = 5
if z % 2 == 0: # False
print("checking " + str(z))
print("z is even")
if-else condition
The if-else
condition adds an additional step in the decision-making process compared to the simple if
statement. The beginning of an if-else
statement operates similar to a simple if
statement; however, if the condition is false, instead of printing nothing, the indented expression under else
will be printed.
if condition:
expression
else:
expression
Example of if-else
Continuing our previous example, what if you want to print 'z is odd' when the if
condition is false? In this case, you can simply add another condition, which is the else
condition. If you run it with z
equal to 5, the condition is not true, so the expression for the else statement gets printed out.
z = 5
if z % 2 == 0:
print("z is even")
else:
print("z is odd")
z is odd
if-elif-else condition
The most complex of these conditions is the if-elif-else
condition. When you run into a situation where you have several conditions, you can place as many elif
conditions as necessary between the if
condition and the else
condition.
if condition:
expression
elif condition:
expression
else:
expression
Example one of if-elif-else condition
Below is an example of where you want different printouts for numbers that are divisible by 2 and 3.
Here, since z
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.
z = 3
if z % 2 == 0:
print("z is divisible by 2")
elif z % 3 == 0:
print("z is divisible by 3")
else:
print("z is neither divisible by 2 nor by 3")
z is divisible by 3
Example two of if-elif-else condition
In the below example, you define two variables room
and area
. You then construct if-elif-else
and if-else
conditions each for room
and area
, respectively.
In the first condition, you check if
you are looking in the kitchen, elif
you are looking in the bedroom, else
you are looking around elsewhere. Depending on the value of the room
variable, the satisfied condition is executed.
Similarly, for the area
variable, you write an if
and else
condition and check whether the area
is greater than 15 or not.
# Define variables
room = "bed"
area = 14.0
# if-elif-else construct for room
if room == "kit":
print("Looking around in the kitchen.")
elif room == "bed":
print("Looking around in the bedroom.")
else:
print("Looking around elsewhere.")
# if-elif-else construct for area
if area > 15:
print("Big place!")
else:
print("Pretty small.")
When we run the above code, it produces the following result:
Looking around in the bedroom. Pretty small.
To learn more about elif statements in Python, please see this video from our course, Intermediate Python.
This content is taken from DataCamp’s Intermediate Python course by Hugo Bowne-Anderson.