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Python

Posted by Kittisiri Napachotsiri
Kittisiri Napachotsiri
1,538 Points

Why don't just use clean_list = messy_list ?

why don't we just use clean_list = messy_list instead of clean_list = messy_list[:]

1 Answer

Christian Mangeng
Christian Mangeng
16,598 Points

Hi,

using clean_list = messy_list does not actually create a copy of messy_list. Instead, it causes clean_list to reference to the same object as messy_list, meaning that if you change one of them, the other will change too. Sometimes an independent copy needs to be made, that's why clean_list = messy_list[:] is used.

Kittisiri Napachotsiri
Kittisiri Napachotsiri
1,538 Points

Thanks a lot. At first, I thought when I use A = B it would put the value of B into A And when I change A, it won't affect B.

However, it seems I misunderstood the concept.

I guess it's because Python is an object-oriented language? Or does this situation works with all language?

Christian Mangeng
Christian Mangeng
16,598 Points

Actually, both cases are true, it depends on whether the object you copy is immutable or mutable. What you say is correct e.g. for strings, as they are immutable, but lists are mutable objects. So copies of strings can be made simply with a = b, but the same won't work for lists.

Kittisiri Napachotsiri
Kittisiri Napachotsiri
1,538 Points

Wow! Again, thanks a lot. You really clear things up.