Python functools partialmethod() Function

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The Python partialmethod() function is similar to the partial function. The main difference is partialmethod() is used within the class method.

The function allows us to create a new function with a specific number of arguments predefined from another function. A partial() function is used to specify a function by reducing the number of parameters it requires.

Syntax

Following is the syntax for the partialmethod() function.

functools.partialmethod(func, /, *args, **keywords)

Parameters

The parameters for the partialmethod() function are listed below −

• / : This indicates that all parameters must be specified positionally.
• *args : This is the positional argument used to set in advance for the new function.
• **keywords : This is the keyword argument used to predefined the new function.

Return Value

This function returns a new partial method descriptor.

Example 1

In the below example, we double the given values by multiplying the predefined values using the partialmethod() function.

import functools
class Calculator:
    def multiply(x, y, z):
       return y*z
    double = functools.partialmethod(multiply, 4)
a = Calculator()
print(a.double(10))
print(a.double(20))

Output

The result is generated as follows −

40
80

Example 2

This code defines the Adder class with an add method that sums three numbers using the partialmethod() function. The add_ten method pre fills the first argument with 10, with the remaining arguments provided during the method call.

import functools
class Adder:
    def add(self, x, y, z):
        return x + y + z
    add_ten = functools.partialmethod(add, 10)
adder = Adder()
print(adder.add_ten(10, 20))  
print(adder.add_ten(15, 25))

Output

The code is generated as follows −

40
50

Example 3

Here, we are defining the power class with power method that rises a base to an exponent. When square is called using partialmethod() function then it returns the square of the given number.

import functools
class Power:
  def power(self, base, exponent):
    return base**exponent
  square = functools.partialmethod(power, exponent = 4)
power = Power()
print(power.square(16))
print(power.square(8))

Output

The output is obtained as follows −

65536
4096