Functional programming in Python

functional programming in Python

Higher order functions

a higher order function is a function that passes a function as a parameter. It's a bit like a delegate in C #, personally.

def Add (x,y,f):         return f (x) + f (y)    print   Add ( -18,11,abs)

It will do so:

ABS ( -18) + ABS (11)

The result would be:

29

map () function

map () is a Python built-in high-order function that receives a function f and a list, and then, by putting the function f on each element of the list in turn, gets a new list and returns.

def f (x):     return x* xprint#every element in the list will go through the f (X) method

The result will be:

[1, 4, 9, 10, 25, 36, 49]

reduce () functionthe reduce () function is also a high-order function built into Python. The reduce () function receives a parameter similar to map (), a function f, a list, but behaves differently from map (), and reduce () the incoming function f must receive two parameters, and reduce () calls function f repeatedly on each element of the list, and returns the final result value.

def f (x, y):         return x* y    print#1*2*3*4

The result will be this:

24

What if you want to give the initial value? Need this:

  def F (A, B        ): return a +    bprint#1+2+3+4+10. The third parameter here is the initial value. 

The result would be:

20

 filter () functionThe filter () function is another useful high-order function built into Python, and the filter () function receives a function f and a list, the function of which is to judge each element and return True or False, filter () automatically filters out non-conforming elements based on the result of the decision, returning a new list of eligible elements.

def is_odd (x):        return x%2==1    Print filter (is_odd,[1,2,3,4,5,6,7])

The result is:

[1, 3, 5, 7]

  Custom Sort Functions

The python built-in sorted () function can sort the list:

Sorted ([36, 5, 12, 9, 21])
[5, 9, 12, 21, 36]

But sorted () is also a high-order function, which can receive a comparison function to implement a custom sort, the definition of the comparison function is to pass in two elements to be compared x, Y, if x should be in front of y, return-1, if X should be ranked after Y, return 1. returns 0 if x and y are equal.

Functional programming in Python