Python's reduce,map, selfie,

One, reduce (function,iterable), it is the same form as the map () function. However, the parameter function must have two parameters .

The reduce () function is a cumulative calculation of the result continuation and the next element of the sequence.

Cases

>>>def Add (x, y): # Two number added
... return x + y
...
>>> reduce (add, [1,2,3,4,5]) # calculation list and: 1+2+3+4+5
15
>>> reduce (lambda x, Y:x+y, [1,2,3,4,5]) # using lambda anonymous functions
15




Twomap (function,iterable)is to use each element in the list for a function.

1. Return value:

Python 2.x returns a list.

Python 3.x returns an iterator.
so there are two basic ways to get a map return value in Python3:
①print (Map (f,iter)) #这里的f代表函数, Iter represents an iterative object.
② uses a For loop.


Cases
①m = map (lambda x:x + 1, [1, 2, 3])
Print (list (m)) #结果为: [5, 7, 9]

② provides two lists to add the list data to the same location
>>> map (lambda x, y:x + y, [1, 3, 5, 7, 9], [2, 4, 6, 8, 10])
[3, 7, 11, 15, 19]




Three zip The function accepts any number of iterated objects as arguments, packages the corresponding elements in the object into a tuple, and returns an iterator to the Zip object.
Cases
LT1 = [' A ', ' B ', ' C ']
LT2 = [1, 2, 3]
LT3 = [' A ', ' B ', ' C ']
result = List (Zip (LT1, LT2, LT3))
Print (Result) #输出结果: [(' A ', 1, ' a '), (' B ', 2, ' B '), (' C ', 3, ' C ')]



Fourfilter ()The function is used to filter the sequence, filter out elements that do not meet the criteria, and return a new list of eligible elements.
Filter receives two parameters, the first is a function, the second is a sequence, each element of the sequence is passed as a parameter to the function, and then returns True or False, and finally the element that returns true is placed in the new list.
Grammar:Filter (function, iterableble)

Cases
func = lambda x:x% 2 = = 1
Print (List (func, [i])) #输出结果: [1, 3]

Python's reduce,map, selfie,