Python's zip function

Python's zip function

Transfer from http://www.cnblogs.com/frydsh/archive/2012/07/10/2585370.html

The ZIP function accepts any number of sequences (including 0 and 1) as parameters, returning a tuple list. The specific meaning is not good to express in words, directly look at the example:

1. Example 1:

x = [1, 2, 3]y = [4, 5, 6]z = [7, 8, 9]xyz = Zip (x, y, z) print xyz

The result of the operation is:

[(1, 4, 7), (2, 5, 8), (3, 6, 9)]

From this result, we can see the basic operation of the ZIP function.

2. Example 2:

x = [1, 2, 3]y = [4, 5, 6, 7]xy = Zip (x, y) print xy

The result of the operation is:

[(1, 4), (2, 5), (3, 6)]

From this result, we can see how the length of the zip function is handled.

3. Example 3:

x = [1, 2, 3]x = Zip (x) print X

The result of the operation is:

[(1,), (2,), (3,)]

From this result you can see how the ZIP function works when there is only one parameter.

4. Example 4:

x = Zip () print X

The result of the operation is:

[]

From this result, you can see how the zip function works without parameters.

5. Example 5:

x = [1, 2, 3]y = [4, 5, 6]z = [7, 8, 9]xyz = Zip (x, y, z) u = Zip (*xyz) print U

The result of the operation is:

[(1, 2, 3), (4, 5, 6), (7, 8, 9)]

It is generally thought that this is a unzip process, and its operating mechanism is this:

Before running Zip (*xyz), the value of XYZ is: [(1, 4, 7), (2, 5, 8), (3, 6, 9)]

Then, Zip (*xyz) is equivalent to zip ((1, 4, 7), (2, 5, 8), (3, 6, 9))

So the result is: [(1, 2, 3), (4, 5, 6), (7, 8, 9)]

Note: Using *list/tuple in a function call means separating the list/tuple, passing it as a positional parameter to the corresponding function (provided that the corresponding function supports an indefinite number of positional parameters)

6. Example 6:

x = [1, 2, 3]r = Zip (* [x] * 3) Print R

The result of the operation is:

[(1, 1, 1), (2, 2, 2), (3, 3, 3)]

It operates in such a way that:

[x] generates a list of lists that have only one element x

[x] * 3 generates a list of lists, it has 3 elements, [x, X, X]

The meaning of Zip (* [x] * 3) is clear, zip (x, x, x)

Python's zip function