# Partial Functions in Python

Partial functions allow us to fix a certain number of arguments of a function and generate a new function. In this article, we will try to understand the concept of Partial Functions with different examples in Python.

## What are Partial functions and the use of partial functions in Python?

Partial functions in Python is a function that is created by fixing a certain number of arguments of another function. Python provides a built-in module called functools that includes a function called partial that can be used to create partial functions. The `partial` function takes a callable (usually another function) and a series of arguments to be pre-filled in the new partial function. This feature is similar to bind in C++.

### How do you implement a partial function in Python?

Partial functions support both positional and keyword arguments to be used as fixed arguments.

Example 1

In this example, we use default values to implement the partial function. The default values start replacing variables from the left. In the example, we have pre-filled our function with some constant values of a, b, and c. And g() just takes a single argument i.e. the variable x.

## Python3

 `from` `functools ``import` `partial`   `# A normal function` `def` `f(a, b, c, x):` `    ``return` `1000``*``a ``+` `100``*``b ``+` `10``*``c ``+` `x`   `# A partial function that calls f with` `# a as 3, b as 1 and c as 4.` `g ``=` `partial(f, ``3``, ``1``, ``4``)`   `# Calling g()` `print``(g(``5``))`

Output:

`3145`

Example 2

In the example, we have used pre-defined value constant values in which we have assigned the values of c and b and add_part() takes a single argument i.e. the variable a.

## Python3

 `from` `functools ``import` `*`   `# A normal function` `def` `add(a, b, c):` `    ``return` `100` `*` `a ``+` `10` `*` `b ``+` `c`   `# A partial function with b = 1 and c = 2` `add_part ``=` `partial(add, c ``=` `2``, b ``=` `1``)`   `# Calling partial function` `print``(add_part(``3``))`

Output:

`312`

### Uses of partial functions

• Integration with Libraries: Partial functions can be used to customize the behavior of third-party functions or methods by providing partial arguments and can be used to integrate it with other libraries.
• Simplifying Callbacks: Partial functions can be used to create specialized callback handlers by fixing some callback-specific parameters and providing a cleaner interface for the rest of the code.
• Parameter Fixing: : Partial functions can be very useful when we have a function with multiple parameters and we frequently want to use it with some parameters fixed. Instead of repeatedly passing those fixed parameters, we can create a partial function and call it with the remaining arguments.
• Reducing Duplication: If we are using the same arguments for a function in various places, creating a partial function with those fixed arguments can help to reduce code duplication and maintenance efforts.
• Default Arguments: Python’s built-in `functools.partial` can be used to set default values for function arguments.
• Reusability of code: Partial functions can be used to derive specialized functions from general functions and therefore help us to reuse our code.

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