What Does the Tilde (~) Operator Do in Python?

Understanding the Python Tilde Operator

The tilde (~) operator in Python is a unary operator used for bitwise inverse or negation. It operates on integers and returns the complement of the input bits.

Usage for Integers

When applied to integers, the tilde operator flips all the bits of the twos-complement representation of the integer. The result is interpreted again as a twos-complement integer. This makes ~x equivalent to (-x) - 1.

For example:

>>> ~5
-6

Using Inversion for Custom Classes

The reified form of the ~ operator is operator.invert. Classes can support this operator by implementing an __invert__(self) method.

For instance:

import operator

class Foo:
    def __invert__(self):
        print('invert')

x = Foo()
operator.invert(x)  # Prints 'invert'
~x  # Also prints 'invert'

This operator can be useful for classes where it makes sense to have a "complement" or "inverse" of an instance that is also an instance of the same class.

Additional Uses

Beyond integer inversion, the tilde operator is sometimes used in combination with string slicing to perform tasks on both sides of a string or list. For example, it can be used to check if a string is palindromic:

def is_palindromic(s):
    return all(s[i] == s[~i] for i in range(len(s) // 2))

Overall, the tilde operator is a versatile tool that can be used for both bitwise inversion and custom class inversion in Python.

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