Python Basics: Built-in function zip,map,filter

One, zip

Zip, is to combine the two lists, if you want to loop 2 list at the same time, you can use the zip, will help you rotate the two list

For example: L1=[1,2,3,4,5]l2=['a','b','C','D','e'] forA, binchZip (l1,l2):Print(A, b)#The result is
1 A
1 A
3 C
3 C
5 e

If the length of the two list is inconsistent, it is based on a small length

For example: L1=[1,2,3,4]l2=['a','b','C','D','e'] forA, binchZip (l1,l2):Print(A, b)#To get the result is
1 A
2 b
3 C
4 D

Second, map

Loop Call function

def my (num):     return  = [1,2,3,4,5,6,7,8,9= List (map (My,lis))#map parameter The first is the function name, the second is the content to loop, the result is a map Object address, so to cast the next print(res)# with the list will eventually call the contents of the LIS loop my function, res=[' 1 ', ' 2 ', ' 3 ', ' 4 ', ' 5 ' , ' 6 ', ' 7 ', ' 8 ', ' 9 ']

defmy (num1,num2):return(num1,num2) Lis= [1,2,3,4,5]lis1=['a','b','C','D']res= List (map (MY,LIS,LIS1))#The first of the map parameter is the function name, the rest is to loop the content, the function has several parameters, it is necessary to write a few variables, the return result is a Map object address, so to use the list to cast under thePrint(RES)#Eventually, the contents of the LIS and Lis1 are looped through the My function, res=[(1, ' a ') (2, ' B ') (3, ' C ') (4, ' d ')]

Third, filter

Filter and map on the surface is the same, is the loop call function, the difference is: filter is filtered, it will be the content of the loop into the function, the result is true corresponding content returned

def even (num):     if num%2==0:        return  True    return= [ 1,2,3,4,5,6,7,8,9= filter (even,lis)print('filter. ', List (res))  #filter is reserved only, returning the data as true. After the LIS loop is dropped into the even function, the data in the LIS that can return true will be printed, so the end result is 2,4,6,8
#如果改程序用map的话, the function returns what it will print and the end result is false,true,false,true .....

Python Basics: Built-in function zip,map,filter