Increment id during loop in list of collections

Question

I try to increment a list at each iteration of a loop :

ads = []
page = {}
page['titre'] = "Title here"
page['nombre_pages'] = 396

i = 1 
total = 3

while i <= total:
    print(i)
    page['id'] = i
    ads.append(page)
    i += 1

this return

[{'titre': 'Title here', 'nombre_pages': 396, 'id': 3}, {'titre': 'Title here', 'nombre_pages': 396, 'id': 3}, {'titre': 'Title here', 'nombre_pages': 396, 'id': 3}]

I don't understand why the same id 3 times and not id:1, id:2, id:3

When print page['id'] is ok (increment), ads.append(page['id']) is available too.

Can you help ?

Thanks

You're modifying and appending the same `page` dict each time. — Daniel Roseman, Oct 23 '18 at 12:27
Possible duplicate of [How to copy a dictionary and only edit the copy](https://stackoverflow.com/questions/2465921/how-to-copy-a-dictionary-and-only-edit-the-copy) — depperm, Oct 23 '18 at 12:28

score 1 · Accepted Answer · answered Oct 23 '18 at 12:30

you're only creating a single "page" object, i.e. by doing:

page = {}

and referring to it from several index locations in ads. you probably want to be doing something closer to:

ads = []

i = 1 
total = 3

while i <= total:
    print(i)
    page = {}
    page['titre'] = "Title here"
    page['nombre_pages'] = 396
    page['id'] = i
    ads.append(page)
    i += 1

or slightly more idiomatically:

ads = []
total = 3
for i in range(total):
    ads.append({
        'nombre_pages': 396,
        'titre': "Title here",
        'id': i,
    })

Increment id during loop in list of collections

1 Answers1