Example of a list loop statement usage in Python

This example describes the use of the list loop statement in Python. Share to everyone for your reference. The specific usage analysis is as follows:

One of the great features of Python is its parsing of lists, which provides a compact way to map a list to another list by applying a function to each element in the list.
Instance
Copy the Code code as follows:

A = [' Cat ', ' window ', ' defenestrate ']
For X in a:
Print x, Len (x)
For x in [1, 2, 3]: print x, # iteration Loop through a list:for in
A = [' Cat ', ' window ', ' defenestrate ']
For x in a[:]: # Make a slice copy of the entire list
If Len (x) > 6:a.insert (0, X)

Print a

Operation Result:
Copy the Code code as follows:

Cat 3
Window 6
Defenestrate 12
1 2 3 [' defenestrate ', ' Cat ', ' window ', ' defenestrate ']

To manipulate according to the length of the array:
Copy CodeThe code is as follows:

A = [' Mary ', ' had ', ' a ', ' little ', ' lamb ']
For I in range (Len (a)):
Print I, A[i]

Operation Result:
Copy CodeThe code is as follows:

0 Mary
1 had
2 A
3 Little
4 Lamb

Copy the Code code as follows:

words = [' A ', ' B ', ' C ', ' D ', ' E ']
For word in words:
Print Word

Operation Result:
Copy CodeThe code is as follows:

A
B
C
D
E

List Parsing Introduction:
Copy the Code code as follows:

>>> Li = [1, 9, 8, 4]
>>> [elem*2 for Elem in Li]
[2, 18, 16, 8]
>>> Li
[1, 9, 8, 4]
>>> Li = [elem*2 for Elem in Li]
>>> Li
[2, 18, 16, 8]

For the sake of understanding it, let's look from right to left. Li is a list that will be mapped. Python loops through each element in the LI. Do the following for each element: first temporarily assigns its value to the variable Elem, then Python applies the function elem*2 for the calculation, and finally appends the result to the list to be returned.

It is important to note that parsing the list does not change the original list.

It is safe to assign the parse result of a list to the variable to which it is mapped. Don't worry about a competitive situation or any weird things happening. Python creates a new list in memory, and when parsing the list is complete, Python assigns the result to the variable.

Hopefully this article will help you with Python programming.

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