Consider the following code.
with open('filename.txt', 'r') as f:
var = [element for element in f.readlines()][3]
This question concerns the internals of Python, rather than the result.
Does Python calculate all the elements of the indexes in the entire list of [element for element in f.readlines()]
, or does Python just calculate all of the elements until the third index?
CodePudding user response:
It calculates all of them. You can verify with something like this:
>>> [(i, print(i)) for i in range(3)][1]
0
1
2
(1, None)
This isn't really "internal", because this is well-defined behaviour and list comprehensions can have side-effects (even if they shouldn't).