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Collate all files in directory from lowest integer to highest, then start from lowest

April 6, 2022

In a directory I will have any number of files. All of the file names will contain ‘R1’ or ‘R2’, ‘R3’ etc within. for example thisfile_R1.csv. The ‘R’ numbers in this directory will not always be consistent, so sometime the lowest may be ‘R3’ and run sequentially to ‘R15’.

I need a way for python to start at the lowest integer of the R* files in the directory, then loop through to the last ‘R’ integer, as a way to edit files from lowest to highest, sequentially.

procdir = r"C:\Users\processed"

collected = os.listdir(procdir)
for f in collected:
    #if fnmatch.fnmatch(f, '*R*.csv'):
   if "R*.csv" in collected:

>Solution :

You can use the glob module to select only the file names that match your pattern:

import glob

procdir = r"C:\Users\processed"
files = glob.glob(rf"{procdir}\*R*.csv")

Then, use sorted() with a key argument to capture the number and sort on that number:

files_sorted = sorted(files, key=lambda x: int(re.findall(r"R(\d+)", x)[-1]))

The lambda expression takes the file path, finds the pattern R followed by any number of digits and captures only the digits, and then converts the last entry in that list to an integer. The sorting is done based on this integer, so you end up with the correct order.

If your directory had the files:

files = [r"C:\Users\processed\file_R1.csv",
         r"C:\Users\processed\file_R100.csv",
         r"C:\Users\processed\file_R13.csv",
         r"C:\Users\processed\file_R3.csv",
         r"C:\Users\processed\file_R30.csv"]

you’d get the sorted files like so:

['C:\\Users\\processed\\file_R1.csv',
 'C:\\Users\\processed\\file_R3.csv',
 'C:\\Users\\processed\\file_R13.csv',
 'C:\\Users\\processed\\file_R30.csv',
 'C:\\Users\\processed\\file_R100.csv']