Python logical operators are used to combine or modify conditions and return a Boolean result (True or False). They are commonly used in conditional statements to control the flow of a program based on multiple logical conditions.
Let's see an example which demonstrates how Python logical operators and, or, and not work using Boolean variables.
a, b, c = True, False, True
# AND: Both conditions must be True
if a and c:
print("Both a and c are True (AND condition).")
# OR: At least one condition must be True
if b or c:
print("Either b or c is True (OR condition).")
# NOT: Reverses the condition
if not b:
print("b is False (NOT condition).")
Output
Both a and c are True (AND condition). Either b or c is True (OR condition). b is False (NOT condition).
Explanation:
- a and c returns True because both values are True.
- b or c returns True because at least one value is True.
- not b reverses False to True, so the condition executes.
The following table summarizes the Python logical operators, their purpose, syntax and examples:
| Operator | Description | Syntax | Example |
|---|---|---|---|
| and | Returns True if both the operands are true | x and y | x>7 and x>10 |
| or | Returns True if either of the operands is true | x or y | x<7 or x>15 |
| not | Returns True if the operand is false | not x | not(x>7 and x> 10) |
Truth Table for Logical Operators
A truth table shows how logical operators behave for all possible combinations of Boolean values (True and False). It helps in clearly understanding the output of AND, OR, and NOT operations.
AND Operator
The Boolean AND operator returns True if both the operands are True else it returns False.
Example 1: Below example shows how the logical AND (and) operator works by checking if all conditions are true before executing a statement.
a = 10
b = 10
c = -10
if a > 0 and b > 0:
print("The numbers are greater than 0")
if a > 0 and b > 0 and c > 0:
print("The numbers are greater than 0")
else:
print("Atleast one number is not greater than 0")
Output
The numbers are greater than 0 Atleast one number is not greater than 0
Example 2: The code checks if all variables a, b, and c evaluate to True, printing a message accordingly.
a = 10
b = 12
c = 0
if a and b and c:
print("All the numbers have boolean value as True")
else:
print("Atleast one number has boolean value as False")
Output
Atleast one number has boolean value as False
Note: If the first expression is evaluated to be false while using the AND operator, then the further expressions are not evaluated.
OR Operator
The Boolean OR operator returns True if either of the operands is True.
Example 1: Below example demonstrates the logical OR (or) operator, where the condition becomes true if at least one of the given expressions evaluates to True.
a = 10
b = -10
c = 0
if a > 0 or b > 0:
print("Either of the number is greater than 0")
else:
print("No number is greater than 0")
if b > 0 or c > 0:
print("Either of the number is greater than 0")
else:
print("No number is greater than 0")
Output
Either of the number is greater than 0 No number is greater than 0
Example 2: The code checks if any of the variables a, b, or c has a boolean value as True; if so, it prints "At least one number has boolean value as True".
a = 10
b = 12
c = 0
if a or b or c:
print("Atleast one number has boolean value as True")
else:
print("All the numbers have boolean value as False")
Output
Atleast one number has boolean value as True
Note: If the first expression is evaluated to be True while using or operator, then the further expressions are not evaluated.
NOT Operator
The Boolean NOT operator works with a single boolean value. If the boolean value is True it returns False and vice-versa.
Example: Below code checks if a is divisible by either 3 or 5, otherwise, it prints a message indicating that it is not.
a = 10
if not a:
print("Boolean value of a is True")
if not (a % 3 == 0 or a % 5 == 0):
print("10 is not divisible by either 3 or 5")
else:
print("10 is divisible by either 3 or 5")
Output
10 is divisible by either 3 or 5
Order of Precedence of Logical Operators
When multiple logical operators are used in a single expression, Python evaluates them from left to right and applies short-circuit evaluation. This means Python stops evaluating further conditions as soon as the result is determined.
def check(x):
print("Method called for value:", x)
return x > 0
a = check
b = check
c = check
if a(-1) or b(5) or c(10):
print("At least one of the numbers is positive")
Output
Method called for value: -1 Method called for value: 5 Atleast one of the number is positive
Explanation:
- a(-1) returns False, so Python checks the next condition.
- b(5) returns True, so Python stops evaluating further conditions.
- c(10) is never executed due to short-circuit behavior of or.
