Shulou(Shulou.com)05/31 Report--

Today, I will talk to you about how to assign values and deep and shallow copies in the python list, which may not be well understood by many people. in order to make you understand better, the editor has summarized the following contents for you. I hope you can get something according to this article.

First create a list

A = [1, 2, 3], 4, 5, 6]

I. assignment

B=aa [0] [1] = 'tom'print (a) print (b) results:

[1, 'tom', 3], 4, 5, 6]

[1, 'tom', 3], 4, 5, 6]

B=ab [0] [1] = 'tom'print (a) print (b) result: [1,' tom', 3], 4 tom', 5 print 6] [1, 'tom', 3], 4 tom', 5 6] Summary: whether the assignment is to change a list or b list, as long as one of them is changed, the other will change, because an and b share a piece of memory. No new memory is created, they are the same, and they point to the same memory area. Shallow copy [:] or copy ()

B=a.copy () b [0] [1] = 'tom'print (a) print (b) result:

[1, 'tom', 3], 4, 5, 6]

[1, 'tom', 3], 4, 5, 6]

B=a.copy () a [0] [1] = 'tom'print (a) print (b) result: [1,' tom', 3], 4 tom', 5 tom', 6]

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

[[1, 2, 3], 'tom', 5,6]

B=a.copy () a [1] = 'tom'print (a) print (b) result:

[[1, 2, 3], 'tom', 5,6]

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

Summary: from the above code, we can see that shallow copy is to reopen up a piece of memory, copy the first layer of data, and not copy internal child elements.

In this code, the b list re-opens up a block of storage elements [b [0], 4pd5pcm6], which is the first layer of content.

Then the location of b [0] points to the memory location pointed to by a [0].

Third, deep copy using the copy function

Reopen a piece of memory to store all the contents of the copy list. A set and b set do not affect each other.

Import copya= [[1Jing 2jue 3], 4Jing 5Jer 6] b=copy.deepcopy (a) a [1] = 'tom'print (a) print (b) results:

[[1, 2, 3], 'tom', 5,6]

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

Import copya= [[1Jing 2jue 3], 4Jing 5Jer 6] b=copy.deepcopy (a) b [1] = 'tom'print (a) print (b) results:

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

[[1, 2, 3], 'tom', 5,6]

Import copya= [[1Jing 2 Jue 3], 4 Jing 5 Jing 6] b=copy.deepcopy (a) b [0] [1] = 'tom'print (a) print (b) result

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

[1, 'tom', 3], 4, 5, 6]

[1, 'tom', 3], 4, 5, 6]

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

The copy function can also be shallowly copied:

Import copya= [[1Jing 2jue 3], 4Jing 5Jer 6] b=copy.copy (a) a [0] [1] = 'tom'print (a) print (b) results:

[1, 'tom', 3], 4, 5, 6]

[1, 'tom', 3], 4, 5, 6]

After reading the above, do you have any further understanding of how to make assignments and deep and shallow copies in the python list? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

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