CODEWITHSUNDEEP
pythonclass
user1780294
user1780294

Reputation: 11

Changing variable in instance not working when appending to list - Python

Why is this not working as expected (at least for me)? I can't figure why.

class Fred:
    def __init__(self):
          self.a=0

fred=Fred()
lista=[]

for i in range(5):
    fred.a=i
    lista.append(fred)

for i in lista:
    print(str(i.a))

All I get is 5 times the number 4 and not from 0 to 4. Any comments? Thanks

Upvotes: 1

Views: 114

Answers (2)

icktoofay
icktoofay

Reputation: 129011

You've got one Fred instance and keep adding that one instance to the list, changing its a property while you do that. Adding to the list does not copy the Fred object; it just adds another reference to the same object. You can get your expected behavior by creating a new Fred inside each iteration of the loop.

Upvotes: 0

Jay Taggart
Jay Taggart

Reputation: 137

What is happening is that the reference to Fred is being overwritten each time you loop in the for i in range(5). If you move the fred=Fred() inside that loop and create a new object each time, then you should see the expected result.

Upvotes: 1

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