What is Python equivalent of the ! operator?

In some languages like C / C++, the "!" symbol is used as a logical NOT operator. !x returns true if x is false, else returns false. The equivalent of this "!" operator in Python is the not keyword, which also returns True if the operand is false and vice versa.

Basic Usage with Boolean Values

Example with True Value

In the following example, the variable operand_X holds a boolean value True. After applying the not operator, it returns False −

operand_X = True
print("Input: ", operand_X)

result = not operand_X
print('Result: ', result)

Input:  True
Result:  False

Example with False Value

For a False value, the not operator returns True −

operand_X = False
print("Input: ", operand_X)

result = not operand_X
print('Result: ', result)

Input:  False
Result:  True

Using not with Different Data Types

String Example

In Python, non-empty strings are considered True. The not operator returns False for non-empty strings −

X = "python"
print("Input: ", X)

result = not X
print('Result: ', result)

Input:  python
Result:  False

Empty List Example

Empty lists are treated as False in Python. Due to this, the not operator returns True for empty list objects −

li = []
print("Input: ", li)

result = not li
print('Result: ', result)

Input:  []
Result:  True

Using not with Comparison Expressions

The not operator can also be applied to comparison expressions −

print("not(10 < 20): ", not(10 < 20))
print("not(10 > 20): ", not(10 > 20))
print("not(True == True): ", not(True == True))

not(10 < 20):  False
not(10 > 20):  True
not(True == True):  False

Truthiness in Python

Python considers the following values as False: False, 0, "" (empty string), [] (empty list), {} (empty dict), and None. All other values are considered True.

# Examples of falsy values
print("not 0:", not 0)
print("not '':", not "")
print("not None:", not None)

# Examples of truthy values  
print("not 5:", not 5)
print("not 'hello':", not "hello")
print("not [1, 2]:", not [1, 2])

not 0: True
not '': True
not None: True
not 5: False
not 'hello': False
not [1, 2]: False

Conclusion

The Python not operator is equivalent to the ! operator in C/C++. It returns the opposite boolean value of its operand and works with Python's truthiness concept, making it useful for testing empty collections, None values, and boolean expressions.