Doing a assignment in python for loop

Question

I was trying to do an assignment operation in python single line for loop like

[a[i]=b[i] for i in range(0,len(b))]

This seems wrong. Is there a way I can use assignment operation in python single line for loop?

Btw., what you are using is not a for loop but a list comprehension. — jotasi, Jun 01 '17 at 09:18
Do `a` and `b` have the same length? And what is your use-case? Maybe there's an even better way (without loops or comprehensions). — MSeifert, Jun 01 '17 at 09:42

score 1 · Answer 1 · answered Jun 01 '17 at 09:18

1

You are mixing two paradigms here, that of loop and list comprehension. The list comprehension will be

a = [x for x in b]

answered Jun 01 '17 at 09:18

Elan

1

or why not `a = b[:]` – jeffery_the_wind Jun 01 '17 at 09:41
1

Does the same, but I think OP is trying to learn list comprehension as an alternative to looping over list. This explicitly conveys the idea. – Elan Jun 01 '17 at 13:43

Arun · Answer 2 · 2017-06-01T09:29:15.390

1

Copy lists can be done in many ways in Python.

edited Jun 01 '17 at 09:29

answered Jun 01 '17 at 09:21

Arun

https://stackoverflow.com/questions/2612802/how-to-clone-or-copy-a-list – jeffery_the_wind Jun 01 '17 at 09:41

score 1 · Answer 3 · answered Jun 01 '17 at 09:21

1

No need for a loop. You can use a slice assignment:

a[0:len(b)]= b

answered Jun 01 '17 at 09:21

Aran-Fey

score 1 · Answer 4 · answered Jun 01 '17 at 09:38

You could use:

[a.__setitem__(i, b[i]) for i in range(0,len(b))]

the __setitem__ is the method that implements index-assignment. However doing a list comprehension only because of side-effects is a big no-no.

You could simply use slice-assignment:

a[:len(b)] = b

score 0 · Answer 5 · answered Jun 01 '17 at 09:47

0

in python 3 it can be done by:

a = b.copy()

answered Jun 01 '17 at 09:47

R.A.Munna

5 Answers5