What is the python assignment statement?

Assignment statement
In Python, the main assignment operator is the equal sign (=)
Assignment does not directly assign a value to a variable. Objects are passed by reference. Regardless of whether the variable is newly created or already exists, a reference to the object is assigned to the variable.

In C language, the assignment statement can be regarded as an expression and can return a value. But in Python, assignment statements do not return values. This makes such a statement illegal

>>> y = (x = x + 1) # assignments not expressions! File "<stdin>", line 1y = (x = x + 1)^SyntaxError: invalid syntax>>> if (a = 3):

SyntaxError: invalid syntax

Compared to ordinary assignment, it is not just a change in writing, the most significant change is that the first object is only processed once.
Python does not support pre/post increment/decrement operations such as x or --x
Multiple assignment

>>> x, y, z = 1, 2, 'a string'>>> x1
>>> y2
>>> z'a string'>>> x, y, z
(1, 2, 'a string')

When assigning, the objects on both sides of the equal sign They are all regarded as tuples

Using the method of multiple assignment, you can directly exchange table values ​​without using intermediate variables

>>> x , y = 1, 2
>>> x, y
(1, 2)>>> x, y = y, x>>> x, y
(2, 1)

The following table is the copy operation and annotation

Operation	Explanation
a=10	Basic form
a,b = 10,20	Tuple assignment
[a,b] = [10,20]	List assignment( Positional)
a,b = 'AB'	Sequence assignment (general)
a,b = [10,20]	Sequence assignment (generality)
a,*b = 'hello'	Extended sequence unpacking (python3 Unique to medium)
a = b = c = 10	Multiple target assignment
a = 1	Enhanced assignment

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