For map(), its prototype is: map(function, sequence), which is to perform function operations on each element in the sequence.
For example, the previous a, b, c = map(int, raw_input().split()) means to convert the input a, b, c into integers. Another example:
a = ['1','2','3','4'] print map(list,a) print map(int,a)
The first map converts each element in list a into a list, and the second map converts each element in a is an integer.
For zip(), the prototype is zip(*list), list is a list, and zip(*list) returns a tuple, such as:
list = [[1,2,3],[4,5,6],[7,8,9]] t = zip(*list) print t
Output: [(1, 4, 7), (2, 5, 8), (3, 6, 9)]
x = [1,2,3,4,5] y = [6,7,8,9,10] a = zip(x,y) print a
Output: [(1, 6), (2, 7), (3, 8), (4, 9), (5, 10)]
Here are some additions:
[python] >>> list = [[0,1,2],[3,1,4]] >>> [sum(x) for x in list] [3, 8] >>> map(sum,list) [3, 8]
If you want to get the sum of each column, you need to use zip(*list) to unzip the list first and get a tuple list, in which the i-th element The group contains the i-th element of each row:
[python] >>> list = [[0,1,2],[3,1,4]] >>> zip(*list) [(0, 3), (1, 1), (2, 4)] >>> [sum(x) for x in zip(*list)] [3, 2, 6] >>> map(sum,zip(*list)) [3, 2, 6]
The following example is about how zip and unzip (actually zip and * are used together) work :
[python] >>> x=[1,2,3] >>> y=[4,5,6] >>> zipped = zip(x,y) >>> zipped [(1, 4), (2, 5), (3, 6)] >>> x2,y2=zip(*zipped) >>> x2 (1, 2, 3) >>> y2 (4, 5, 6) >>> x3,y3=map(list,zip(*zipped)) >>> x3 [1, 2, 3] >>> y3 [4, 5, 6]
For more related articles introducing the operation methods of map() and zip() in python, please pay attention to the PHP Chinese website !

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