Question

I am trying to make a duplicate list of lists and change one element to another within the nested lists of the duplicate list but am having some trouble.
How I made the duplicate list:

order = [['yhjK', 'F'], 'gap', ['bcsA', 'F'], ['bcsB', 'F'], ['bcsZ', 'F'], 'gap', ['yhjK', 'R']]
#order_1 = list(order) #this makes the duplicate list as well
order_1 = []
for x in order:
    order_1.append(x)

How I changed the elements:

for item in order_1:
    for n,i in enumerate(item):
            if i=='R':
                    item[n]='F'
            if i=='F':
                    item[n]='R'

I want to replace all the ‘F’ with ‘R’ and vice versa. This accomplishes that but the original list ‘order’ is changed as well. I only want the second list to be changed and can’t figure out what is the problem with my code.

What I get:

order = [['yhjK', 'R'], 'gap', ['bcsA', 'R'], ['bcsB', 'R'], ['bcsZ', 'R'], 'gap', ['yhjK', 'F']]
order_1 = [['yhjK', 'R'], 'gap', ['bcsA', 'R'], ['bcsB', 'R'], ['bcsZ', 'R'], 'gap', ['yhjK', 'F']]

What I want:

order = [['yhjK', 'F'], 'gap', ['bcsA', 'F'], ['bcsB', 'F'], ['bcsZ', 'F'], 'gap', ['yhjK', 'R']]
order_1 = [['yhjK', 'R'], 'gap', ['bcsA', 'R'], ['bcsB', 'R'], ['bcsZ', 'R'], 'gap', ['yhjK', 'F']]

Thanks everyone!

Answer 1

What you’re doing here is a shallow copy of the list, so when you change the copy, the original changes as well. What you need is deepcopy

import copy
order = [['yhjK', 'F'], 'gap', ['bcsA', 'F'], ['bcsB', 'F'], ['bcsZ', 'F'], 
'gap', ['yhjK', 'R']]
order_1 = copy.deepcopy(order)

# Now changing order_1 will not change order
order_1[1] = ['TEST LIST']
print order[1] # Prints 'gap'
print order_1[1] # Prints '['TEST LIST']