Python update variable referenced in loop

Question

I'm trying to create a bunch of directories. Some of them will fail due to permissions and whatnot and in that case, I would like that directory created in /tmp and then replace the value in the corresponding variable.

import os

ROOT = "/var"
IMG_DIR = "images"
HASH_DIR = "hashes"
TEAM_DIR = "teams"

for some_dir in [IMG_DIR, HASH_DIR, TEAM_DIR]:
    current_path = os.path.join(ROOT, some_dir)
    if not os.path.exists(current_path):
        try:
            os.makedirs(current_path)
        except OSError:
            new_path = os.path.join("/tmp", some_dir)
            # if the error happened in images, update IMG_DIR with the new path
            # if the error happened in hashes, update HASH_DIR with the new path
            # if the error happened in teams, update TEAM_DIR with the new path

IMG_DIR, HASH_DIR and TEAM_DIR will be global vars and are accessed throughout the program. What's the most elegant/Pythonic way to accomplish this?

I'd suggest to place them in settings.py and import them when needed — gogaz
– gogaz, Commented Jan 10, 2019 at 16:31
start with a dict instead, e.g. {'IMG_DIR': 'images', 'HASH_DIR': 'hashes'} etc. — Chris_Rands
– Chris_Rands, Commented Jan 10, 2019 at 16:32

grapes · Accepted Answer · 2019-01-10 16:52:52Z

2

You need something like that:

import os

ROOT = "/var"
my_dirs = {
    'IMG_DIR': "images",
    'HASH_DIR': "hashes",
    'TEAM_DIR': "teams"
}

for name, path in my_dirs.items():
    current_path = os.path.join(ROOT, path)
    if not os.path.exists(current_path):
        try:
            os.makedirs(current_path)
        except OSError:
            new_path = os.path.join("/tmp", path)
            my_dirs[name] = new_path

UPD

If you strictly require update the variables and do not accept dictionary (Why??), you can use following approach:

import os

def create_dir(root: str, path: str) -> str:
    current_path = os.path.join(root, path)
    if not os.path.exists(current_path):
        try:
            os.makedirs(current_path)
        except OSError:
            new_path = os.path.join("/tmp", path)
            # maybe create this directory here?
            return new_path 
    return current_path

ROOT = "/var"
IMG_DIR =  create_dir(ROOT, "images")
HASH_DIR = create_dir(ROOT, "hashes")
TEAM_DIR = create_dir(ROOT, "teams")

edited Jan 10, 2019 at 16:52

answered Jan 10, 2019 at 16:39

grapes

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2 Comments

Craig Over a year ago

I thought about this approach, but the statement my_dirs[name] = current_path only updates the value of the key IMG_DIR within the dictionary my_dirs. The value of the variable IMG_DIR does not change and that's my initial problem. Also I think you mean my_dirs[name] = new_path

Craig Over a year ago

Thanks - I'm editing someone else's code where variables are scattered a few hundred times all over the place, which is why I'm hesitant to use dicts.

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