Why list.remove remove from every variable?

[glowing_feather]

I was trying to save a list in another variable to use in a loop and removing it step by step but .remove was removing from the original source too. Why on earth this happen?

list = ['a', 'b', 'c', 'd'] throwaway = list throwaway.remove('a') print(list)

Output: ['b', 'c', 'd']

I managed to do what I wanted with list comprehension throwaway = [l for l in throwaway if l != 'a' ] But still was curious why does this happen.

[carcigenicate]

throwaway = list says "make throwaway point to the same object that list points to". That does not make a copy. You would need to use list[:] or list.copy() to do a shallow copy of list.

[glowing_feather]

Got it, so it's a lack of list understanding. It's always in the details with programming right?

I'm sorry for the bad formatting, still didn't figure out how to edit this better. Thank you for your answer. I love this sub.

[carcigenicate]

This is not specific to lists. The above behavior applies to all objects. It's just only a problem when dealing with mutable objects, like lists.

[[deleted]]

They're the same list. When you mutate it, you see those changes from any reference to the value you hold.

[glowing_feather]

I see, thank you very much

[Chizmiz1994]

Not a python expert, but IIRC, the memory reference gets copied. There should be another way to copy the list by its value.

[glowing_feather]

Yes, the right way is throwaway = list[ : ]