Python Forum

Hi,

I am getting an TypeError, and not sure why? My goal is to write on the second and third position of a list . I can do it using a for loop but I would like to avoid the for loop by indexing a range of elements directly on the list. How can I do it?

>>>list=[1,3,4,30,10,20]
>>>for i in range(1,3,1):
list[i] = 0

>>>list
[1, 0, 0, 30, 10, 20]
>>>list[1:3] = 1
Traceback (most recent call last):
File "<input>", line 1, in <module>
TypeError: can only assign an iterable

Hmm, I never thought to even try that. The problem is that list[1:3] selects values from index 1 up to index 3 for a total of 2 items. You cannot replace multiple items with a single item. Instead, you need to provide an interable for the interpreter to loop over and replace values.

list[1:3] = [1]

While we're at it, it's inadvisable to use "list" as a variable name. Think of it like a reserved keyword because there's a builtin function called list() and Python replaces it with the variable.

If you want to replace both items with "1",s then something like this:

>>> l = [1,3,4,30,10,20]
>>> l
[1, 3, 4, 30, 10, 20]
>>> l[1:3] = [1] * 2
>>> l
[1, 1, 1, 30, 10, 20]