Python Forum

is parenthesis required around a tuple of literals in a for?

i'm running into this:

Output:
>>> for x in 1,2,3:
...   print(x)
... 
1
2
3
>>> [x for x in 1,2,3]
  File "<stdin>", line 1
    [x for x in 1,2,3]
                 ^
SyntaxError: invalid syntax
>>>

, outside of data structure like eg list it will always make a tuple.

>>> 1, 2
(1, 2)

>>> 'hello', 'world'
('hello', 'world')

So for x in 1,2,3: is just the same as for x in (1,2,3):

In a list is , parsed as separator,then 1, 2, 3 is three separate element and not a tuple.
For it to be a tuple or list inside a list comprehension then have to make it so () [].

>>> [x for x in (1,2,3)]
[1, 2, 3]

>>> [x for x in [1,2,3]]
[1, 2, 3]

so you have to put the , deeper in whatever you want it to be in, because in a comprehension it is already in something that will apply to it.