Unexpected modification of a Python 3 list

Asked May 20 '20 at 11:34

Active May 20 '20 at 11:37

Viewed 24 times

I am new to coding and was trying solve a question on here posed previously. Have a list (lst) of dictionaries. Want to create a new list (newlist) of dictionaries, with the count of identical dictionaries in the original list, in new list as keyed item in each dictionary. My code below adds the count of dictionaries to dictionary of original list and I can't see why.

lst = [{'time': 10, 'stuff': 'abcd'},{'time': 10, 'stuff':'abcd'},{'time': 11, 'stuff': 'bcd'},{'time': 12, 'stuff': 'dc'},{'time': 13, 'stuff': 'ak'},{'time': 11, 'stuff': 'bcd'}]
newlist= []
m = 0
while len(lst)>0 :
    y = lst[0]
    ycount = lst.count(y)
    newlist=newlist + [y]
    newlist[m]['count'] = ycount
    print(f'lst = {lst}\n')
    while y in lst:
        lst.remove(y)
    m += 1
print(f'newlist= {newlist}')

asked May 20 '20 at 11:34

MarkJPD

can you provide sample output. – Avinash Dalvi May 20 '20 at 11:37
1

There's only ever one dict object (for each dict in the list). Assigning it to a new list doesn't create a second copy of it. Modifying it modifies the original. – deceze May 20 '20 at 11:38
Thanks deceze. Have solved problem by using y = copy.deepcopy(lst[0]) to create a truly new dictionary. – MarkJPD May 20 '20 at 12:38

Unexpected modification of a Python 3 list

0 Answers0