Description of the functions of map, reduce, zip, and filter built-in functions in python

Description of the functions of map, reduce, zip, and filter built-in functions in python
Map function usage: map (function, sequence) function: executes function (item) in sequence for items in sequence and returns the List of results.

List1 = [1, 2, 3] list2 = [2, 3, 4] print map (lambda x: x + 1, list1) print map (lambda x, y: x + y, list1, list2) running result: [2, 3, 4] [3, 5, 7]

 

2. reduce function usage: reduce (function, sequence) function: Calls function for sequential iteration of items in sequence

   list1 = [1,2,3]   print reduce(lambda x,y:x+y,list1)

 

Running result: 6 3.zip function usage: zip (function, sequence) function: receives any number of (including 0 and 1) sequences as parameters and returns a tuple list.

List1 = [1, 2, 3] list2 = [2, 3, 4] list3 = [3, 4, 5] list4 = [7] print "zip () ---->", zip () print "zip (list1) ---->", zip (list1) print "zip (list1, list2) ---->", zip (list1, list2) print "zip (list1, list2, list3) ----> ", zip (list1, list2, list3) print" zip (list1, list2, list3, list4) ----> ", zip (list1, list2, list3, list4) # matching result of a long list: zip () ----> [] zip (list1) ----> [(1,), (2,), (3,)] zip (list1, list2) ----> [(1, 2), (2, 3), (3, 4)] zip (list1, list2, list3) ----> [(1, 2, 3), (2, 3, 4), (3, 4, 5)] zip (list1, list2, list3, list4) ----> [(1, 2, 3, 7)]

 

4. filter function usage: filter (function, sequence) function: executes function (item) in sequence for items in sequence ), combine items with the execution result of True into a List/string/tuple (depending on the sequence type)

    list1 = [1,2,3]   print filter(lambda x:x>1,list1)

 

Running result: [2, 3]