"Can only iterable" Python error

Question

Hello my fellow programmers.

I am a fairly new programmer, and now I am facing a great predicament. I am getting the error:

can only assign an iterable

Firstly I don't know what that means.

Secondly I will leave my code for you professionals to critique it:

def num_top(int_lis):
    duplic_int_lis = int_lis
    int_firs= duplic_int_lis [0]
    int_lis[:] = duplic_int_lis [int_firs]

Basically I am trying to find the [0] element in the list and then using that int as an index position to find the integer at that index position.

You are trying to assign an integer (I guess from the name) to a list. As the error says: You can only assign to lists (or slices thereof) an iterable and an integer is not iterable. — Hyperboreus, Nov 06 '13 at 19:30
`duplic_int_lis = int_lis` does not create a duplicate list. — NULL, Nov 06 '13 at 19:33
@RogerPate .. then how can one go about creating a duplicate list? — user2954367, Nov 06 '13 at 19:41
Can you clarify what return value you expect from your function (it currently returns `None`) and what mutation you expect to happen to the input list? Your example `output` could be either of those, but we can't tell which. — Blckknght, Nov 06 '13 at 20:05

Ashwini Chaudhary · Answer 1 · 2013-11-06T19:36:45.980

4

int_lis[:] = duplic_int_lis [int_firs] means assign all the items of duplic_int_lis [int_firs] to int_lis, so it expects you to pass an iterable/iterator on the RHS.

But in your case you're passing it an non-iterable, which is incorrect:

>>> lis = range(10)
>>> lis[:] = range(5) 
>>> lis               #all items of `lis` replaced with range(5)
[0, 1, 2, 3, 4]

>>> lis[:] = 5        #Non-iterable will raise an error.
Traceback (most recent call last):
  File "<ipython-input-77-0704f8a4410d>", line 1, in <module>
    lis[:] = 5
TypeError: can only assign an iterable

>>> lis[:] = 'foobar' #works for any iterable/iterator
>>> lis
['f', 'o', 'o', 'b', 'a', 'r']

As you cannot iterate over an integer, hence the error.

>>> for x in 1: pass
Traceback (most recent call last):
  File "<ipython-input-84-416802313c58>", line 1, in <module>
    for x in 1:pass
TypeError: 'int' object is not iterable

edited Nov 06 '13 at 19:36

answered Nov 06 '13 at 19:31

Ashwini Chaudhary

244,495
58
464
504

okay I got the code working... but now the problem is... nothing mutates... it still returns the original list. – user2954367 Nov 06 '13 at 19:50
@user2954367 Your question isn't clear actually, please provide some examples in the question body. – Ashwini Chaudhary Nov 06 '13 at 19:52
1

@user2954367 Try `int_lis[int_lis[0]]`. – Ashwini Chaudhary Nov 06 '13 at 20:03

score 1 · Answer 2 · answered Nov 06 '13 at 19:30

1

The RHS of a slice-assignment must be an iterable, not a scalar. Consider slice-deleting and then appending instead.

answered Nov 06 '13 at 19:30

Ignacio Vazquez-Abrams

776,304
153
1,341
1,358

2

while technically impeccable i'm afraid i can't upvote an answer that is 98% likely to go over the questioner's head... – Claudiu Nov 06 '13 at 19:31
no that actually makes sense, only thing is... could you explain slice deleting? – user2954367 Nov 06 '13 at 19:46
@user2954367: `del int_lis[:]` This deletes the contents of the list, but leaves the list itself alone. But reading further, it seems that this isn't what you want to do at all. – Ignacio Vazquez-Abrams Nov 06 '13 at 19:49
well that is sort of what I want.. But I want the integer without the [].. for example now when I run the code the result I get is [3]. – user2954367 Nov 06 '13 at 19:55
Then you should return the value instead of mutating the list. – Ignacio Vazquez-Abrams Nov 06 '13 at 19:56
but if I simply return the value... it does return, if I state return (int_lis) .. but it returns the original list if I return (None) – user2954367 Nov 06 '13 at 19:58

score 0 · Answer 3 · answered Nov 06 '13 at 19:36

An iterable is a thing with multiple items that you can iterate through (for example: take the 1st value do something, then the 2nd do something, etc...) Lists, dictionaries, tuples, strings have several items in them and can be used as iterables. As a counterexample: number types don't qualify as iterable.

Remember that computers count from #0 so: if you want the first value of a list you can use

my_list[0]

before you go further I would suggest watching this video about looping. https://www.youtube.com/watch?v=EnSu9hHGq5o

"Can only iterable" Python error

3 Answers3

Linked