[] & () for variables in Python variable assignment

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  explains [] and () for variables in for statement.
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  explains variable assignment.
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  explains iterable unpacking in variable assignment.
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  explains * for iterable unpacking in variable assignment.

You can use zero or more [] and () for one or more variables in a variable assignment as shown below:


mylist = [[[5]]]

v1 = mylist
(v1) = mylist
print(v1) # [[[5]]]

[v1] = mylist
(v1,) = mylist
print(v1) # [[5]]

[[v1]] = mylist
((v1,),) = mylist
print(v1) # [5]

[[[v1]]] = mylist
(((v1,),),) = mylist
print(v1) # 5

mytuple = (((5,),),)

v1 = mytuple
(v1) = mytuple
print(v1) # (((5,),),)

[v1] = mytuple
(v1,) = mytuple
print(v1) # ((5,),)

[[v1]] = mytuple
((v1,),) = mytuple
print(v1) # (5,)

[[[v1]]] = mytuple
(((v1,),),) = mytuple
print(v1) # 5

mylist = [0, 1, [2, 3, [4, 5]]]

v1 = mylist
print(v1) # [0, 1, [2, 3, [4, 5]]]

[v1, v2, v3] = mylist
(v1, v2, v3) = mylist
print(v1, v2, v3) # 0 1 [2, 3, [4, 5]]

[v1, v2, [v3, v4, v5]] = mylist
(v1, v2, (v3, v4, v5)) = mylist
print(v1, v2, v3, v4, v5) # 0 1 2 3 [4, 5]

[v1, v2, [v3, v4, [v5, v6]]] = mylist
(v1, v2, (v3, v4, (v5, v6))) = mylist
print(v1, v2, v3, v4, v5, v6) # 0 1 2 3 4 5

mytuple = (0, 1, (2, 3, (4, 5)))

v1 = mytuple
print(v1) # (0, 1, (2, 3, (4, 5)))

[v1, v2, v3] = mytuple
(v1, v2, v3) = mytuple
print(v1, v2, v3) # 0 1 (2, 3, (4, 5))

[v1, v2, [v3, v4, v5]] = mytuple
(v1, v2, (v3, v4, v5)) = mytuple
print(v1, v2, v3, v4, v5) # 0 1 2 3 (4, 5)

[v1, v2, [v3, v4, [v5, v6]]] = mytuple
(v1, v2, (v3, v4, (v5, v6))) = mytuple
print(v1, v2, v3, v4, v5, v6) # 0 1 2 3 4 5

*Only one *variable can be used in each [] and ().


mylist = [0, 1, [2, 3, [4, 5]]]

v1 = mylist
*v1, = mylist
*(v1), = mylist
print(v1) # [0, 1, [2, 3, [4, 5]]]

[v1, *v2, v3] = mylist
(v1, *v2, v3) = mylist
print(v1, v2, v3) # 0 [1] [2, 3, [4, 5]]

[v1, *v2, [*v3, v4, v5]] = mylist
(v1, *v2, (*v3, v4, v5)) = mylist
print(v1, v2, v3, v4, v5) # 0 [1] [2] 3 [4, 5]

[v1, *v2, [*v3, v4, [v5, *v6]]] = mylist
(v1, *v2, (*v3, v4, (v5, *v6))) = mylist
print(v1, v2, v3, v4, v5, v6) # 0 [1] [2] 3 4 [5]

mytuple = (0, 1, (2, 3, (4, 5)))

v1 = mytuple
print(v1)
# (0, 1, (2, 3, (4, 5)))

*v1, = mytuple
*(v1), = mytuple
print(v1) # (0, 1, (2, 3, (4, 5)))

[v1, *v2, v3] = mytuple
(v1, *v2, v3) = mytuple
print(v1, v2, v3) # 0 [1] (2, 3, (4, 5))

[v1, *v2, [*v3, v4, v5]] = mytuple
(v1, *v2, (*v3, v4, v5)) = mytuple
print(v1, v2, v3, v4, v5) # 0 [1] [2] 3 (4, 5)

[v1, *v2, [*v3, v4, [v5, *v6]]] = mytuple
(v1, *v2, (*v3, v4, (v5, *v6))) = mytuple
print(v1, v2, v3, v4, v5, v6) # 0 [1] [2] 3 4 [5]

*A [] and () cannot be used for a function parameter.


def func([p]): pass
# SyntaxError: invalid syntax

def func((p)): pass
def func((p,)): pass
# SyntaxError: Function parameters cannot be parenthesized

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