Usage of python Partial Function partial

Directory 1, What is a partial function partial2, the role of a partial function 3, the syntax of a partial function 4, Case 1 Case 2

1. What is the partial function partial

python provides a function with fixed properties for functions

2. The role of partial function

Fix some parameters of a function (that is, set the default value) and return a new function

3. The Grammar of Partial Functions

To use partial functions, you must first import from functools import partial


Function format: partial(func, *args, **kwargs)

func Represents the function name *args : func Indefinite length parameters of functions **kwargs : func Keyword parameters of the function

4. Cases

Case 1

from functools import partial


bin2dec = partial(int, base=2)  #  Put  int  Set the conversion of to 2 It's binary, here  base  Yes  int  The function represents the parameters of the binary system. 
print(bin2dec('0b10001') ) # 17
print(bin2dec('10001'))  # 17

hex2dec = partial(int, base=16)  #  Put  int  Set the conversion of to 16 Binary system 
print(hex2dec('0x67'))  # 103
print(hex2dec('67'))  # 103
 

Case 2

partial_max = partial(max, 100)
print(partial_max(1, 2, 99))  # 100

Above is for max() Function sets 1 default argument 100 Returns 1 new function when we pass in the parameter (1, 2, 99) There is actually one default value in the parameter 100 , equivalent to (100, 1, 2, 99) So the maximum value obtained is 100

These applications of partial functions seem simple, but they are very useful and can be implemented well DRY Principle, save programming costs.