CODEWITHSUNDEEP
pythonreferencedeep-copyshallow-copy
user
user

Reputation: 2103

In python, is a function return a shallow or deep copy?

In python, if I have 

x = y

any modification to x will also modify y, and I can do 

x = deepcopy(y)

if I want to avoid modifying y while working on x

Say, instead, that I have:

myFunc():
    return y

def main():
    x = myFunc()

Is it still the case that modifying x will modify y, or since it is a return from another function it will be like a deepcopy?

Upvotes: 11

Views: 11848

Answers (2)

Aeroblop
Aeroblop

Reputation: 290

It will be a shallow copy, as nothing has been explicitly copied.

def foo(list):
    list[1] = 5
    return list

For example:

>>> listOne = [1, 2]
>>> listTwo = [3, 4]
>>> listTwo = listOne
>>> foo(listTwo)
[1, 5]
>>> listOne
[1, 5]

Upvotes: 8

shx2
shx2

Reputation: 64318

In python everything is a reference. Nothing gets copied unless you explicitly copy it.

In your example, x and y reference the same object.

Upvotes: 21

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