Question

In Python, I want to list all files in a set of directories. The best I’d like to get is a list. But at most I managed to make a nested list:

pics = os.path.expanduser('~/Pictures')
all_pics = [(d, os.listdir(d)) for d in os.listdir(pics)]

result:

[('folder1', ['file1', 'file2', ...]), ('folder2', ['file1', ...]), ...]

what I want:

[('folder1' 'file1'), ('folder1', 'file2'), ..., ('folder2', 'file1'), ...]

What I would like to get is a simple plain list, doesn’t matter of what (can be of tuples), just so that it hasn’t nested things, and I need no nested cycles in the code that parses it.

How can I do this with list comprehensions? Doing this gives me a product of 2 sets (dir names and filenames) which is wrong:

[(d, f) for f in os.listdir(os.path.join(pics, d)) for d in os.listdir(pics)]

Answer 1

You got the order of the for-loops wrong. It should be

all_pics = [(d, f)
            for d in os.listdir(pics)
            for f in os.listdir(os.path.join(pics, d))]

Outermost loop first, innermost loop last.

I wonder why you didn’t get a NameError for d.