Python nested loop

Question

Hello I am new to python and have a question about the best/pythonic way to do nested loops.

I want to go put each directory in an array with a nested array of the file contained in a that directory.

I have been looking at pythons arrays, dicts, sets and tupples and not sure of the best way to do this

[ Note I just want to do this for one level not recursively through all directories ]

Currently I have a function that adds all the files of sub-directories to an array, but now I need to return their parent folder too.

Thanks in advance

    def getffdirs():

    filedirs = []

    path = os.curdir

    for d in os.listdir(path):      

        if os.path.isdir(d):
            print("Entering " + d)

            curPath = os.path.join(path, d)
            for f in os.listdir(curPath):      

                if os.path.isfile(f):
                    print("file " + f)  
                    filedirs.append(f)     
    return filedirs

If you're going to use this for anything other than learning I would suggest using os.walk — Jeff
– Jeff, Commented Jan 25, 2012 at 0:53
In general, I agree, but what if you only want a single level? — Steve Tjoa
– Steve Tjoa, Commented Jan 25, 2012 at 1:29
Hey @jeff As I said I was new to python, I looked at os.walk but thought it might be overkill for one directory level. Would os.walk be better ? — Keith
– Keith, Commented Jan 25, 2012 at 8:18
@Keet: os.walk is the only correct solution. One level or 100 levels. — S.Lott
– S.Lott, Commented Jan 25, 2012 at 13:24
@Keet no it's not overkill because os.walk will return a generator object (very cool/efficient python tool) For example foo = os.walk() to get the generator object and levelOne = foo.next() for the first level list. Two lines of code... not bad. — Jeff
– Jeff, Commented Jan 25, 2012 at 16:54

yurib · Accepted Answer · 2012-01-25 01:44:48Z

1

i'd use a dictionary for this purpose, the keys would be directories and the values lists of files:

def getffdirs():

  dirs = {}
  path = os.curdir
  for d in os.listdir(path):      

    if os.path.isdir(d):
        print("Entering " + d)
        dirs[d] = [] # add directory with empty list

        curPath = os.path.join(path, d)
        for f in os.listdir(curPath):      

            if os.path.isfile(f):
                print("file " + f)  
                dirs[d].append(f) # add files to appropriate directory
  return dirs

to access the data:

for dir,files in dirs.items(): # notice the call to dirs.items(), thats what was missing.
  print "directory: ",dir
  print "files:"
  for f in files:
    print f

edited Jan 25, 2012 at 1:44

answered Jan 25, 2012 at 0:49

yurib

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1 Comment

Keith Over a year ago

Thank for that. That seems like what I am after but I get a 'ValueError: too many values to unpack' error. Any ideas ?

Steve Tjoa · Accepted Answer · 2012-01-25 01:14:56Z

1

EDIT: If you want a dictionary,

EDIT 2: If you want to omit hidden directories,

from os import listdir, curdir
from os.path import isfile, isdir, join

filedirs = dict((d, [f for f in listdir(d) if isfile(join(d,f))]) 
                for d in listdir(curdir) if isdir(d) and d[0] != '.')

Original:

Is this what you're looking for?

filedirs = [[f for f in os.listdir(d) if os.path.isfile(os.path.join(d,f))]
            for d in os.listdir('.') if os.path.isdir(d)]

edited Jan 25, 2012 at 1:14

answered Jan 25, 2012 at 0:53

Steve Tjoa

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1 Comment

Keith Over a year ago

Thanks for that, your original solution only returned the files as I had already, but both were interesting approaches ! I think you're right, dictionary's are the way to go.

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