Vfrdtyky

I created a copy of a list.
When an item was removed from one copy - it was removed from the original as well.

a = ['alpha', 'beta', 'gamma', 'delta']

b = a



b.remove('alpha')



print 'A list is', a

print 'B list is', b

How should I create an independent copy of the list, that will not impact the original?

Late addition

To understand the reason for this mistake - one should refer to the difference between Shallow Copy and Deep Copy Python documentation - 8.17. copy

The difference between shallow and deep copying is only relevant for compound objects (objects that contain other objects, like lists or class instances):

• A shallow copy constructs a new compound object and then (to the extent possible) inserts references into it to the objects found in the original.


• A deep copy constructs a new compound object and then, recursively, inserts copies into it of the objects found in the original.

You can use in-built copy module.

import copy

a = ['alpha', 'beta', 'gamma', 'delta']

# it will perform the shallow copy

b = copy.copy(a)



b.remove('alpha')



print 'A list is', a

print 'B list is', b

For Python3.x. Though, copy module is available in Python3.x

a = ['alpha', 'beta', 'gamma', 'delta']

b = a.copy()



b.remove('alpha')



print('A list is', a)

print('B list is', b)

Hope this helps