Using booleans in an if statement in Python

# Using booleans in an if statement in Python

Use the is operator to check for a boolean value in an if statement, e.g. if variable is True:.

The is operator will return True if the condition is met and False otherwise.

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variable = True

# ✅ check if a variable has a boolean value of True
if variable is True:
    # 👇️ this runs
    print('The boolean is True')

# ------------------------------------------

# ✅ check if a variable is truthy
if variable:
    # 👇️ this runs
    print('The variable stores a truthy value')

The first example checks if the variable stores a True boolean value.

You should use the is operator when you need to check if a variable stores a boolean value or None.

Use the equality operators (equals == and not equals !=) when you need to check if a value is equal to another value, e.g. 'abc' == 'abc'.

In short, use the is operator with built-in constants like True, False and None.

# Checking for False or a Falsy value

You can use the same approach when checking for False or a falsy value in an if statement.

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variable = False

if variable is False:
    # 👇️ this runs
    print('The boolean is False')

if not variable:
    # 👇️ this runs
    print('The variable stores a falsy value')

# Checking for a Truthy Value in an if statement

Here is how we would check for a truthy value in an if statement.

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variable = True

if variable:
    # 👇️ this runs
    print('The variable stores a truthy value')

The falsy values in Python are:

• constants defined to be falsy: None and False.
• 0 (zero) of any numeric type
• empty sequences and collections: "" (empty string), () (empty tuple), [] (empty list), {} (empty dictionary), set() (empty set), range(0) (empty range).

Here are some examples.

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if 'hello':
    print('this runs ✅')

if ['a', 'b']:
    print('This runs ✅')

if '':
    print('this does NOT run ⛔️')

if 0:
    print('this does NOT run ⛔️')

if not X returns the negation of if X. So with if not X, we check if X stores a falsy value.

You will often have to use multiple conditions in a single if statement.

You can do that by using the boolean AND or boolean OR operators.

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if True and True:
    print('This runs ✅')

if True and False:
    print('This does NOT run ⛔️')

# --------------------------------------

if True or False:
    print('This runs ✅')

if False or False:
    print('This does NOT run ⛔️')

The first two examples use the boolean AND operator and the second two examples use the boolean or operator.

In other words, both conditions have to be met for the if block to run.

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if True and True:
    print('This runs ✅')

if True and False:
    print('This does NOT run ⛔️')

When using the boolean or operator, either of the conditions has to be met for the if block to run.

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if True or False:
    print('This runs ✅')

if False or False:
    print('This does NOT run ⛔️')

If the expression on the left or right-hand side evaluates to a truthy value, the if block runs.

I've also written an article on how to check for multiple conditions in an if statement.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• Styling multiline 'if' statements in Python
• Check if all/any elements in List meet condition in Python
• Using f-string for conditional formatting in Python
• Find the index of Elements that meet a condition in Python
• SyntaxError: invalid syntax in if statement in Python [Fix]
• Get the first item in a list that matches condition - Python
• Remove elements from a List based on a condition in Python