How can I search sub-folders using glob.glob module?

There's a lot of confusion on this topic. Let me see if I can clarify it (Python 3.7):

1. glob.glob('*.txt') :matches all files ending in '.txt' in current directory
2. glob.glob('*/*.txt') :same as 1
3. glob.glob('**/*.txt') :matches all files ending in '.txt' in the immediate subdirectories only, but not in the current directory
4. glob.glob('*.txt',recursive=True) :same as 1
5. glob.glob('*/*.txt',recursive=True) :same as 3
6. glob.glob('**/*.txt',recursive=True):matches all files ending in '.txt' in the current directory and in all subdirectories

So it's best to always specify recursive=True.

In Python 3.5 and newer use the new recursive **/ functionality:

configfiles = glob.glob('C:/Users/sam/Desktop/file1/**/*.txt', recursive=True)

When recursive is set, ** followed by a path separator matches 0 or more subdirectories.

In earlier Python versions, glob.glob() cannot list files in subdirectories recursively.

In that case I'd use os.walk() combined with fnmatch.filter() instead:

import os
import fnmatch

path = 'C:/Users/sam/Desktop/file1'

configfiles = [os.path.join(dirpath, f)
    for dirpath, dirnames, files in os.walk(path)
    for f in fnmatch.filter(files, '*.txt')]

This'll walk your directories recursively and return all absolute pathnames to matching .txt files. In this specific case the fnmatch.filter() may be overkill, you could also use a .endswith() test:

import os

path = 'C:/Users/sam/Desktop/file1'

configfiles = [os.path.join(dirpath, f)
    for dirpath, dirnames, files in os.walk(path)
    for f in files if f.endswith('.txt')]

To find files in immediate subdirectories:

configfiles = glob.glob(r'C:\Users\sam\Desktop\*\*.txt')

For a recursive version that traverse all subdirectories, you could use ** and pass recursive=True since Python 3.5:

configfiles = glob.glob(r'C:\Users\sam\Desktop\**\*.txt', recursive=True)

Both function calls return lists. You could use glob.iglob() to return paths one by one. Or use pathlib:

from pathlib import Path

path = Path(r'C:\Users\sam\Desktop')
txt_files_only_subdirs = path.glob('*/*.txt')
txt_files_all_recursively = path.rglob('*.txt') # including the current dir

Both methods return iterators (you can get paths one by one).