Python copy function details (list,array)

Python copy() function explained (list,array)

list

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The python variable name is equivalent to the tag name list2 = list1, a direct assignment that essentially points to the same memory value.

A change in either variable (list1 or list2) affects the other.

>>> list1=[1,2,3,4,5,6]
>>> list2=list1
>>> list1[2]=88
>>> list1
[1, 2, 88, 4, 5, 6]
>>> list2
[1, 2, 88, 4, 5, 6]

And list3 and list4 are copy operations of list1 by slicing, each pointing to a new value.

Arbitrarily changing the value of list3 or list4 will not affect the others.

array

There is a slight difference between the array type and the list type when copying data.

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An array slice is a view of the original array, which means that the data is not copied and any modifications on the view are reflected directly on the source array.

array1, array2, array3, array4 actually point to the same memory value, and any modification to one of these variables will modify the values of the others.

If you want to get a copy of the array slice instead of a view, you need to explicitly perform the copy operation function copy().

array5 = () # A copy of the original array1
array6 = array[1:4].copy() # slide prepared for microscopyarray[1:4]replication

Then, modifying array5 or array6 will not affect array1

Python dictionary copy function

Functions of copy

Make a new copy of the current dictionary (not the same memory address as the original)

Usage of copy

Usage.

() ->This function takes no arguments，Returns an identical dictionary with different memory addresses
In [33]: old_dict = {'name' : 'insane' , 'age' : 33}
In [34]: new_dict = ld_dict.copy()
In [35]: id(new_dict) != id(old_dict)
Out[35]: True

real combat

# coding:utf-8
fruits = {
    'apple': 30,
    'banana': 50,
    'pear': 100
}
real_fruits = ()
print(real_fruits)
real_fruits['orange'] = 50
real_fruits.update({'cherry': 100})
print(real_fruits)
print('Original fruits:', fruits)
real_fruits['apple'] = real_fruits['apple'] - 5
print(real_fruits)
real_fruits['pear'] -= 3
print(real_fruits)
real_fruits.clear()
print(real_fruits)
print('The next day...')
real_fruits = ()
print(real_fruits)

{'apple': 30, 'banana': 50, 'pear': 100}
{'apple': 30, 'banana': 50, 'pear': 100, 'orange': 50, 'cherry': 100}
original (document etc)fruits： {'apple': 30, 'banana': 50, 'pear': 100}
{'apple': 25, 'banana': 50, 'pear': 100, 'orange': 50, 'cherry': 100}
{'apple': 25, 'banana': 50, 'pear': 97, 'orange': 50, 'cherry': 100}
{}
the morrow。。。
{'apple': 30, 'banana': 50, 'pear': 100}
Process finished with exit code 0

summarize

The above is a personal experience, I hope it can give you a reference, and I hope you can support me more.