s={['list']}
Gives error as below:
Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unhashable type: 'list'
s=set(['list'])
However above works fine. Why?
Asked
Active
Viewed 41 times
0
Shubham S. Naik
- 341
- 1
- 4
- 14
-
3The first example should be a `SyntaxError` since you can't define a set that way. You can use either `{}` or `set()` to define a set. – busybear Jul 30 '18 at 16:47
-
Did you mean `s = {['list']}`. In python 3.6.0 your code gives a SyntaxError. But this gives the error you posted. – CDspace Jul 30 '18 at 16:49
-
It was a typo. Corrected the same – Shubham S. Naik Jul 30 '18 at 17:03
2 Answers
2
Your first example should be giving you a SyntaxError.
{['list']} is a set containing a list which raises an error because lists are not hashable.
set(['list']) is a set built from an iterable that happens to be a list. The equivalent expression using curly braces would be {'list'}, which works fine because strings are hashable.
Patrick Haugh
- 59,226
- 13
- 88
- 96
1
The first example is not valid because lists are unhashable.
{['list']} is read as a set containing a single item of type list, but lists cannot be used as set items or keys in python, so you get an error.
The closest analogue would be to use a tuple {('list')}, since tuples are hashable, but it seems more likely that you just want the string, in which case you should write:
s = {'list'}
The second example is valid python syntax.
It calls the set constructor on a list of items to get a set of those items.
Ollin Boer Bohan
- 2,296
- 1
- 8
- 12