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pythonvariablesinstancebindunbind
Nick Tran
Nick Tran

Reputation: 27

Python: How to I unbind a variable from instance in a class?

In class, let's say I have an instance

self.my_instance=6

Then, in a method, say I have something like

my_variable=self.my_instance

Every time I change my_variable to some other value, self.my_instance changes its value also, and this is not what I want. I want to modify my_variable without affecting self.my_instance. This can be quite frustrating and confusing in large programs too.

Thank you!

Upvotes: 0

Views: 1047

Answers (1)

zondo
zondo

Reputation: 20336

When you say my_variable = self.myinstance, my_variable is now just an alias to the object that self.myinstance refers to. To make it a separate object, you can use slicing:

my_variable = self.myinstance[:]

Using self.myinstance[:] means to take all objects from the beginning to the end which means everything. Since it is a slice, however, it returns a copy so this is a common way to get a copy of a list.

This works in your case because my_variable is a list, but if it is a dictionary, for instance, you can use the copy module:

import copy

my_variable = copy.copy(self.myinstance) # Shallow copy

or

my_variable = copy.deepcopy(self.myinstance) # Deep copy

Dictionaries also have the .copy() method for shallow copies.

Upvotes: 2

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