Using Python to create incrementing folder names

Question

I am trying to place all files within a directory into it's own individual folder. When trying to declare the variable 'folders' I enumerate the list of files and try to append the enumerated list number to the end of the folder name, so the folders would look something like... FOLDER_1, FOLDER_2, FOLDER_3, where the trailing digit is generated from enumeration of the files in the directory.

However my code below lists them all as 'FOLDER_0' and then hits an overwrite error, my increment doesn't seem to be working, any direction into what I am doing wrong would be much appreciated.

PATH = "C:/Temp/"

def main(): 
    files = [ join(PATH, f) for f in listdir(PATH) if isfile(join(PATH, f)) ]

    for i, f in enumerate (files):
        folders = [ PATH+"FOLDER_"+str(i)+"/" for f in files ]

What would you like to have in `folders` after the for-loop? Now you iterate through files but use `f` nowhere, i.e. the last line is equivalent to folders = [ PATH+"FOLDER_"+str(i)+"/" ] * len(files), which may not be what you want. Also, you are using the variable `f` twice (outer and inner loop), which really may cause problems. — DrV, Jun 16 '14 at 18:06
Each time you perform the `for` cycle, a new variable `folders` is created. You must initialize an empty variable `folders = []` before the `for` cycle and then use the `list.append()` method or the `+=` operator to add a new item: `folders.append([ PATH+"FOLDER_"+str(i)+"/" for f in files ])` — s3n0, Mar 05 '19 at 13:37
However, I see more discrepancies. Why do you use `enumerate` if you do not need it? You can also use: `for i in range(len(files))` or make a one-line function as for the `files` variable: `folders = [ PATH+"FOLDER_"+str(i)+"/" for i in range(len(files)) ]` — s3n0, Mar 05 '19 at 13:53

score 1 · Accepted Answer · edited May 23 '17 at 11:52

It is not really clear what your end goal is, but from what you have shown in your code and written in your question I think I can take a stab at it.

To start python uses zero based indexing, so the first value corresponding to the first item in enumerate will be 0.
Next your for loop is equivalent to doing something like this:

folders = [PATH + "FOLDER_" + str(len(files))] * len(files)

So for...

files=["file1", "file2"]

you would get...

folders=["FOLDER_1", "FOLDER_1"]

This is likely where the "overwrite error" is indirectly coming form. If you tried to create every folder in folders you get an OSError telling you that you are creating a folder you just created.

If you wanted to create a folder for each file you had in a directory, I would try to modify your code into this direction:

PATH = "C:/Temp/"

def main():
    files = [join(PATH, f) for f in listdir(PATH) if isfile(join(PATH, f))]
    folders = [join(PATH, "FOLDER_{}".format(i + 1)) for i, _ in enumerate(files)]
    ...

And then if you are going to create all the folders in folders check they don't already exist

Thank you so much MrAlias, your solution is exactly what I was looking for, and much more efficient than my original method. Cheers! — MikG, Jun 16 '14 at 19:56

Using Python to create incrementing folder names

1 Answers1