open a text file using list()

[Pedroski55]

I saw this today for opening a text file:

with open(file) as f:
    lines = list(f)

Never seen that before, I only know readlines(), which delivers the same thing, I think!?

Is it OK to do this? How can it work?

[DeaD_EyE]

f is iterable, and it yields lines, where the line ending is not stripped away.
list(f) consumes the iterator.


Example with a finite generator:

def generator():
    yield 1
    yield 2
    yield 3


# now we want everything from generator
values = list(generator())

[noisefloor]

In addition to Dead_EyE: as explicitly stated Python's documentation, the build-in list-class can take an iterable as the argument and return a list from the iterable.

The file object created by the open function is iterable, which is also shown in the Python tutorial. That list(f) works is even explicitly mentioned right there, next to the information that list(f) and f.readlines() do the same thing.

If you have some time to spare, maybe it's a good idea to take another dive into Python's tutorial.

Regards, noisefloor