Question

I build

totalset = {} 

and extract the file names from folders A, B, C, D by

for file_name in (os.listdir(full_subdir_name)):
    full_file_name = os.path.join(full_subdir_name, file_name)

Now I want to build something called namelist that contains all the file names, and I could traverse all the files in the folders through:

for file in namelist[A]:
    blabla...

for file in namelist[B]:
    blabla.. .  

What should I do?

Answer 1

You should probably use a “list comprehension”. Here is an example of how you could do it:

lst_names = [os.path.join(full_subdir_name, n) for n in os.listdir(full_subdir_name)]

So then you would build the full namelist something like this. First you should set up a list of names.

# example using Windwows filenames
# note that we use "raw strings" with r'' so the backslash will not be weird
lst_names = [r'C:\Users\steveha\Desktop', r'C:\Users\steveha\Documents', r'C:\Users\steveha\Music']

# example using Mac or Linux filenames
lst_names = ['/home/steveha/Desktop', '/home/steveha/Documents', '/home/steveha/Music'

Once you have lst_names set up with your names, build the full namelist:

namelist = {}

for full_subdir_name in lst_names:
    namelist[full_subdir_name] = [os.path.join(full_subdir_name, n) for n in os.listdir(full_subdir_name)]

Personally I think it would be easier to read with a shorter variable name than full_subdir_name:

namelist = {}

for f in lst_names:
    namelist[f] = [os.path.join(f, n) for n in os.listdir(f)]