Python Numbers 4

numbers
The Python numbers module provides an abstract hierarchy of numeric types. It defines a set of abstract base classes (ABCs) that describe the various numeric types and their behaviors in Python.

This module is useful for checking whether an object is a number and for creating your own numeric types.

Here’s an example:

>>> import numbers
>>> isinstance(5, numbers.Number)
True
Key Features
Provides abstract base classes for numeric types
Enables type checking for numbers
Allows creation of custom numeric types
Frequently Used Classes and Functions
Object	Type	Description
numbers.Number	Class	Provides an ABC for all numbers
numbers.Complex	Class	Provides an ABC for complex numbers
numbers.Real	Class	Provides an ABC for real numbers
numbers.Rational	Class	Provides an ABC for rational numbers
numbers.Integral	Class	Provides an ABC for integral numbers
Examples
Check whether a number is an instance of a numeric type:

>>> import numbers

>>> isinstance(3.14, numbers.Real)
True
Define a custom numeric type by subclassing:

>>> class RealNumber(numbers.Real):
...     def __float__(self):
...         return 3.14
...
...     # Rest of the implementation here...
Note: For this class to work, it has to provide concrete implementations for all the abstract methods in the numbers.Real abstract base class:

>>> import numbers

>>> numbers.Real.__abstractmethods__
frozenset(
   {
       '__float__',
       '__radd__',
       '__floordiv__',
       ...
       '__pos__',
       '__neg__'}
)
Common Use Cases
Verifying whether a value is of a numeric type
Implementing custom numeric types with specific behaviors
Ensuring type compatibility in numeric computations
Real-World Example
Suppose you want to create a custom numeric type that represents a constant value. You can use the numbers module to ensure your custom type behaves like a real number:

>>> import numbers

>>> class Constant(numbers.Real):
...     def __init__(self, value):
...         self.value = value
...
...     def __float__(self):
...         return float(self.value)
...
...     def __add__(self, other):
...         return Constant(self.value + float(other))
...
...     def __repr__(self):
...         return f"Constant({self.value})"
...
...     # Rest of the implementation here...

>>> c = Constant(10)
>>> c + 5
Constant(15.0)
>>> isinstance(c, numbers.Real)
True
By subclassing numbers.Real, you ensure that your Constant class behaves like a real number, allowing you to integrate it seamlessly with existing numeric operations.