Boolean Expressions in Python

Boolean expressions in Python evaluate to either True or False. They are widely used in conditional statements, loops, and logical operations.

Syntax

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# Boolean values
True
False

# Boolean expressions with comparison operators
x == y  # Equal to
x != y  # Not equal to
x > y   # Greater than
x < y   # Less than
x >= y  # Greater than or equal to
x <= y  # Less than or equal to

# Boolean expressions with logical operators
A and B  # True if both A and B are True
A or B   # True if at least one of A or B is True
not A    # Negates A (True becomes False, False becomes True)

Boolean Values in Python

Python has two Boolean values: True and False. These are case-sensitive, so always use an uppercase T and F.

Return Value

Boolean expressions return either True or False depending on the conditions evaluated.

Examples

1. Basic Boolean Values

In this example, we will print the two Boolean values available in Python.

Python provides True and False as built-in constants. Let’s print them:

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# Printing Boolean values
print(True)
print(False)

Output:

True
False

When you run this code, Python simply prints the Boolean values True and False.

2. Boolean Expressions with Comparison Operators

Comparison operators return a Boolean value based on the relationship between two values.

Here, we compare two numbers using different comparison operators:

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x = 10
y = 20

# Comparison operations
print(x == y)  # Is x equal to y?
print(x != y)  # Is x not equal to y?
print(x < y)   # Is x less than y?
print(x > y)   # Is x greater than y?
print(x <= y)  # Is x less than or equal to y?
print(x >= y)  # Is x greater than or equal to y?

Output:

False
True
True
False
True
False

Each line evaluates a condition. Since x = 10 and y = 20:

  • x == y returns False because 10 is not equal to 20.
  • x != y returns True because 10 is indeed not equal to 20.
  • x < y returns True because 10 is less than 20.
  • x > y returns False because 10 is not greater than 20.
  • x <= y returns True because 10 is less than or equal to 20.
  • x >= y returns False because 10 is not greater than or equal to 20.

3. Boolean Expressions with Logical Operators

Logical operators allow combining multiple Boolean conditions.

Python provides three logical operators:

  • and – Returns True if both conditions are True.
  • or – Returns True if at least one condition is True.
  • not – Negates a Boolean value.
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a = True
b = False

# Logical operations
print(a and b)  # Both must be True
print(a or b)   # At least one must be True
print(not a)    # Negates the value of a

Output:

False
True
False

Here’s what happens:

  • a and b returns False because b is False, and both values must be True for and to return True.
  • a or b returns True because at least one value (a) is True.
  • not a returns False because a is True, and not negates the value.

4. Boolean Expressions in Conditional Statements

Boolean expressions are commonly used in if statements to control program flow.

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x = 15

if x > 10:
    print("x is greater than 10")
else:
    print("x is 10 or less")

Output:

x is greater than 10

The condition x > 10 is True, so the first block executes, printing the message.