In Python, is there any way to write this list comprehension without the "x in" variable (since it is left completely unused)? Same applies to a generator expression. I doubt this comes up very often, but I stumbled onto this a few times and was curious to know.
Here's an example:
week_array = ['']*7
four_weeks = [week_array[:] for x in range(4)]
(Also perhaps, is there a more elegant way to build this?)
I don't believe so, and there is no harm in the x. A common thing to see when a value is unused in this way is to use an underscore as the free variable, e.g.:
[week_array[:] for _ in range(4)]
But it's nothing more than a convention to denote that the free variable goes unused.
No. Both constructs must have an iterator, even if its value is unused.
This is similar to other answers, in that I use map, but what I did uses the same function you are using.
four_weeks = map(lambda i: week_array[:], range(4))
Also, the main advantage compared to using _ for example is that it could already be used (_ is used by gettext often) and it changes its value in to the last item in the iterator. See this example:
[x for x in range(4)]
assert x == 3, 'x should be equal to 3'
