Conditionals in Python

if

statements in Python This is the syntax of a basic

if

statement:

if <condition>:
    youre code

If the condition is

True

, the code will run. Else, if it’s

False

, the code will not run. Here we have some examples: False Condition

x = 5

if x > 9:
    print("Hello, World!")

The condition is

x > 9

and the code is

print("Hello, World!")

. In this case, the condition is

False

, so there is no output. True Condition Here we have another example. Now the condition is

True

:

color = "Blue"

if color == "Blue":
    print("This is my favorite color")

The output is:

"This is my favorite color"

Code After the Conditional Here we have an example with code that runs after the conditional has been completed. Notice that the last line is not indented, which means that it doesn’t belong to the conditional.

x = 5

if x > 9:
    print("Hello!")

print("End")

In this example, the condition

x > 9

is

False

, so the first print statement doesn’t run but the last print statement runs because it is not part of the conditional, so the output is:

End

However, if the condition is

True

, like in this example:

x = 15

if x > 9:
    print("Hello!")

print("End")

The output will be:

Hello!
End

Examples of Conditionals This is another example of a conditional:

favorite_season = "Summer"

if favorite_season == "Summer":
    print("That is my favorite season too!")

In this case, the output will be:

That is my favorite season too!

But if we change the value of

favorite_season

:

favorite_season = "Winter"

if favorite_season == "Summer":
    print("That is my favorite season too!")

There will be no output because the condition will be

False

.

if/else

statements in Python We can add an

else

clause to the conditional if we need to specify what should happen when the condition is

False

. This is the general syntax:

if <condition>:
    youre code
else:
    youre code

Let’s see an example with the

else

clause: True Condition

x = 15

if x > 9:
    print("Hello!")
else:
    print("Bye!")

print("End")

The output is:

Hello!
End

When the condition of the

if

clause is

True

, this clause runs. The

else

clause doesn’t run. False Condition Now the

else

clause runs because the condition is

False

.

x = 5

if x > 9:
    print("Hello!")
else:
    print("Bye!")

print("End")

Now the output is:

Bye!
End

if/elif/else

statements in Python To customize our conditionals even further, we can add one or more

elif

clauses to check and handle multiple conditions. Only the code of the first condition that evaluates to

True

will run. First Condition True

x = 5

if x < 9:
    print("Hello!")
elif x < 15:
    print("It's great to see you")
else:
    print("Bye!")

print("End")

We have two conditions

x < 9

and

x < 15

. Only the code block from the first condition that is

True

from top to bottom will be executed. In this case, the output is:

Hello!
End

Because the first condition is

True

:

x < 9

. Second Condition True If the first condition is

False

, then the second condition will be checked. In this example, the first condition

x < 9

is

False

but the second condition

x < 15

is

True

, so the code that belongs to this clause will run.

x = 13

if x < 9:
    print("Hello!")
elif x < 15:
    print("It's great to see you")
else:
    print("Bye!")

print("End")

The output is:

It's great to see you
End

All Conditions are False If all conditions all

False

, then the

else

clause will run:

x = 25

if x < 9:
    print("Hello!")
elif x < 15:
    print("It's great to see you")
else:
    print("Bye!")

print("End")

The output will be:

Bye!
End

Multiple elif Clauses We can add as many

elif

clauses as needed. This is an example of a conditional with two

elif

clauses:

if favorite_season == "Winter":
    print("That is my favorite season too")
elif favorite_season == "Summer":
    print("Summer is amazing")
elif favorite_season == "Spring":
    print("I love spring")
else:
    print("Fall is my mom's favorite season")

Each condition will be checked and only the code block of the first condition that evaluates to

True

will run. If none of them are

True

, the

else

clause will run.