String assignment in a list in a 'for' loop

Question

I have a list ['1', '2', '3', '4'] and I want to convert it to the following: ['1.0', '2.0', '3.0', '4.0']. In the code below, why does the second attempt work and not the first?

>>> list = ['1', '2', '3', '4']
>>> for element in list:
...     element = element + '.0'
...
>>> print(list)
['1', '2', '3', '4']
>>> for element in range(len(list)):
...     list[element] = list[element] + '.0'
...
>>> print(list)
['1.0', '2.0', '3.0', '4.0']

how could have first attempt worked, you are modifying each element not each list element — Irshad Bhat
– Irshad Bhat, Commented Nov 4, 2014 at 11:36

venpa · Accepted Answer · 2014-11-04 11:35:04Z

2

element is the local variable and assigned only to the current element of list.

In the second case list[element] is assigned to list in which element points to the current index of list.

answered Nov 4, 2014 at 11:35

venpa

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Comments

akoppad · Accepted Answer · 2014-11-04 11:40:54Z

0

You are not updating the list. You merely update the element variable.

answered Nov 4, 2014 at 11:40

akoppad

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Comments

user3919096 · Accepted Answer · 2014-11-04 11:53:13Z

0

new_list = [x + '.0' for x in old_list]

answered Nov 4, 2014 at 11:53

user3919096

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7 Comments

tktk Over a year ago

That's an answer, but not to the question asked.

Philio Over a year ago

This does not provide an answer to the question. To critique or request clarification from an author, leave a comment below their post - you can always comment on your own posts, and once you have sufficient reputation you will be able to comment on any post.

Jake Levi Over a year ago

regardless of not being an answer, thanks, that's really helpful

tktk Over a year ago

@Philio This is very much an answer, and not a comment. You downvote a bad answer, not delete it.

Philio Over a year ago

@Korem you said that it was not an answer to the question asked? Hence I flagged it from review as not answering the right question.

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