Creating directories from two lists

Creating directories from two lists - Printable Version

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Creating directories from two lists - QueenSveta - Jun-22-2018

I have the following namedtuple and List

from collections import namedtuple

firefoxprofile = namedtuple("Profile", ["Name", "Path", "isRelative", "Default"])
jb = firefoxprofile(Name='Jason', Path='Profiles/er5rtak4.Jason', isRelative='1', Default=None)
sr = firefoxprofile(Name='Sarah', Path='Profiles/23mvfqcj.Sarah', isRelative='1', Default=None)

files = ["places.sqlite","key4.db", "logins.json"]

firefoxlisttuple = []
firefoxlisttuple.append(jb)
firefoxlisttuple.append(sr)

I'm using a nested for loop to create the paths to each of the files in the files List.

Example:

for profile in firefoxlisttuple:
    for file in files:
        print("{0}\{1}".format(profile.Path,file))

Output:

Profiles/er5rtak4.Jason/places.sqlite
Profiles/er5rtak4.Jason/key4.db
Profiles/er5rtak4.Jason/logins.json
Profiles/23mvfqcj.Sarah/places.sqlite
Profiles/23mvfqcj.Sarah/key4.db
Profiles/23mvfqcj.Sarah/logins.json

I'm aware that a nested for loop isn't a good idea in terms of preformace. What should I do instead to achieve the same output?

RE: Creating directories from two lists - gontajones - Jun-22-2018

In this case, I think you can use some syntax sugars to "hide" (but not avoid) the for loops.
Maybe using product you can get a better performance (test it for large amount of entries).

myrange = [
    [x for x in firefoxlisttuple],
    [y for y in files],
]
for profile, file in itertools.product(*myrange):
    print("{0}\{1}".format(profile.Path, file))

And if your files array will be the same all the time, you can use direct assignment:

for profile in firefoxlisttuple:
    print("{0}\{1}".format(profile.Path, files[0]))
    print("{0}\{1}".format(profile.Path, files[1]))
    print("{0}\{1}".format(profile.Path, files[2]))

You'll have to analyse what are the lengths of the arrays and check the performance.

RE: Creating directories from two lists - volcano63 - Jun-22-2018

(Jun-22-2018, 02:51 AM)QueenSveta Wrote: ......
I'm using a nested for loop to create the paths to each of the files in the files List.

Example:
for profile in firefoxlisttuple:
    for file in files:
        print("{0}\{1}".format(profile.Path,file))
Output:
Profiles/er5rtak4.Jason/places.sqlite
Profiles/er5rtak4.Jason/key4.db
Profiles/er5rtak4.Jason/logins.json
Profiles/23mvfqcj.Sarah/places.sqlite
Profiles/23mvfqcj.Sarah/key4.db
Profiles/23mvfqcj.Sarah/logins.json
I'm aware that a nested for loop isn't a good idea in terms of preformace. What should I do instead to achieve the same output?

Nothing wrong with nested loops. Of course, if you want to create a list - or list of lists - then list comprehension will give a better performance (not that performance is an issue in your case).

You could have used itertools.product - as advised by @gontajones,

for profile, file in itertools.product(firefoxlisttuple, files):
    print("{0}\{1}".format(profile.Path,file))

but performance-wise it may be even worth (who measures performance when printing Tongue

)

Questioning yourself is an admirable quality, but in that case you are falling into the trap of "Pythonic" objection to loops - which is a false claim, the choice between loop and comprehension is context-specific.

And remember,
Premature optimization is the root of all evil