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Most people do not understand the knowledge points of this article "python modifies global variables without adding global", so the editor summarizes the following contents, detailed contents, clear steps, and has a certain reference value. I hope you can get something after reading this article. Let's take a look at this "python modifies global variables without adding global" article.

Taking the following code as an example, we use the global variable an in the local scope, which needs to be declared using the global keyword. Otherwise, the code will not be available.

A = 100def fun (): global an a + = 100fun () print (a)

But there is also a common situation.

For data types that can be modified, it is not necessary to declare global to modify the data types inside the function:

List1 = [100,200] def fun (): list1.append (300) fun () print (list1)

But if you replace the command to add elements with list stitching:

List1 + = list1 + [300]

Then the code is still not available, and you need to add the keyword global declaration list1 to be available.

To further expand and say:

List1 = [100,200] print (list1, id (list1)) list1 = list1 + [300] print (list1, id (list1)) list1 + = print (list1, id (list1)) list1.append (500) print (list1, id (list1))

For list1 = list1 + [300]

As shown in the figure, list1 = list1 + [300] changes the id of list1, which means that the new list1 is no longer changed by the original list1, but regenerated, or can be understood as a re-assigned list1, but using list1 in the process. The code is not available in the local scope without global, because the list1 in list1 + is not available until a new variable is generated.

List1 + = [400], list1.append (500) does not change the id, but the original variable list1.

But list1 + = [400] No global is not available for the same reason as above

List1.append (500) is available without global, and there is no need to declare global for modification operations within the function that conform to the data types that can be modified.

The above is about the content of this article on "python's method of modifying global variables without adding global". I believe we all have some understanding. I hope the content shared by the editor will be helpful to you. If you want to know more about the relevant knowledge, please follow the industry information channel.

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