Create directories for outputs based on setting

Question

I have a dict with a series of bools to specify if a particular aspect of my program will be run (e.g. settings['A'] and settings['B']).

If they are run the results need to go into an aptly named directory. The directory names (not the entire path) are also stored in the dict (e.g. settings['outputDirNameOut1'] and settings['outputDirNameA'])

In order to create the directories I'm using the following code.

for each in filePathList:
    path = os.path.dirname(each)

    if not os.path.exists(os.path.join(path, settings['outputDirNameOut1'])):
        os.makedirs(os.path.join(path, settings['outputDirNameOut1']))

    if settings['A'] is True and not os.path.exists(os.path.join(path, settings['outputDirNameA'])):
        os.makedirs(os.path.join(path, settings['outputDirNameA']))

    if settings['B'] is True and not os.path.exists(os.path.join(path, settings['outputDirNameB'])):
        os.makedirs(os.path.join(path, settings['outputDirNameThreshold']))

    if settings['C'] is True and not os.path.exists(os.path.join(path, settings['outputDirNameC'])):
        os.makedirs(os.path.join(path, settings['outputDirNameC']))
        os.makedirs(os.path.join(path, settings['outputDirNameOut2']))

    if settings['D'] is True and not os.path.exists(os.path.join(path, settings['outputDirNameOut2'])):
        os.makedirs(os.path.join(path, settings['outputDirNameOut2']))

I'm wondering if there's a simpler, easier to read way to accomplish this.

Answer 1

Any time there's a repeating pattern that's very obvious like this you might consider using another loop, or a function, or some other abstraction mechanism available. To me this also looks like example code - please post the actual code you're using!

So first a few comments:

• x is True isn't very idiomatic unless you really want to check for specifically one of the true values, True. Otherwise just write that as x (keeping in mind that some values like the empty tuple or list are actually falsy.

• Some expressions are repeated in the if test and the body of the if - in those cases you likely want to have a variable to only evaluate the expression once for better readability.

• Consider using some functional idioms like map to make the code more succinct too.

• Take a look at PEP8 for variable naming - in Python it's usually snake case.

So how with that said, how could this all look like?

for path in map(os.path.dirname, file_path_list):
    x = os.path.join(path, settings['outputDirNameOut1'])
    if not os.path.exists(x):
        os.makedirs(x)

    y = os.path.join(path, settings['outputDirNameA'])
    if settings['A'] and not os.path.exists(y):
        os.makedirs(y)

    z = os.path.join(path, settings['outputDirNameB'])
    if settings['B'] and not os.path.exists(z):
        os.makedirs(z)

    a = os.path.join(path, settings['outputDirNameC'])
    if settings['C'] and not os.path.exists(a):
        os.makedirs(a)
        os.makedirs(os.path.join(path, settings['outputDirNameOut2']))

    b = os.path.join(path, settings['outputDirNameOut2'])
    if settings['D'] and not os.path.exists(b):
        os.makedirs(b)

Now you just have to come up with more sensible variable names. Also I have the feeling that the double makedirs in the fourth case is a copy&paste error?

Going with that assumption this can be simplified further:

names = ['outputDirNameOut1', 'outputDirNameA', 'outputDirNameB',
         'outputDirNameC', 'outputDirNameOut2']
dirs = [settings[name] for name in names]
for path in map(os.path.dirname, file_path_list):
    for dir in dirs:
        x = os.path.join(path, dir)
        if not os.path.exists(x):
            os.makedirs(x)

At that point I can't see any more obvious changes.

---

Edit: That assumption doesn't hold and I also skipped some part of the logic. Therefore I'd suggest writing and using a local function:

def foo(name):
    x = os.path.join(path, settings[name])
    if not os.path.exists(x):
        os.makedirs(x)

for path in map(os.path.dirname, file_path_list):
    foo('outputDirNameOut1')

    if settings['A']:
        foo('outputDirNameA')

    if settings['B']:
        foo('outputDirNameB')

    if settings['C']:
        foo('outputDirNameC')
        foo('outputDirNameOut2')

    if settings['D']:
        foo('outputDirNameOut2')