I have a folder with over 100,000 files, all numbered with the same stub, but without leading zeros, and the numbers aren't always contiguous (usually they are, but there are gaps) e.g:
file-21.png,
file-22.png,
file-640.png,
file-641.png,
file-642.png,
file-645.png,
file-2130.png,
file-2131.png,
file-3012.png,
etc.
I would like to batch process this to create padded, contiguous files. e.g:
file-000000.png,
file-000001.png,
file-000002.png,
file-000003.png,
When I parse the folder with for filename in os.listdir('.'): the files don't come up in the order I'd like to them to. Understandably they come up
file-1,
file-1x,
file-1xx,
file-1xxx,
etc. then
file-2,
file-2x,
file-2xx,
etc. How can I get it to go through in the order of the numeric value? I am a complete python noob, but looking at the docs i'm guessing I could use map to create a new list filtering out only the numerical part, and then sort that list, then iterate that? With over 100K files this could be heavy. Any tips welcome!
Thank you all for your suggestions, I will try them all to learn the different approaches. The solution I went for is based on using a natural sort on my filelist, and then iterating that to rename. This was one of the suggested answers but for some reason it has disappeared now so I cannot mark it as accepted!
import os
files = os.listdir('.')
natsort(files)
index = 0
for filename in files:
os.rename(filename, str(index).zfill(7)+'.png')
index += 1
where natsort is defined in http://code.activestate.com/recipes/285264-natural-string-sorting/