list_files.py

import os
import fnmatch

# does not operate recursively
def list_directories(directory, exclude_prefixes=('.',)):
    for f in os.listdir(directory):
        if f.startswith(exclude_prefixes):
            continue
        joined = os.path.join(directory, f)
        if os.path.isdir(joined):
            yield joined

# extensions can be a string or list, can include the preceding . or not
# operates recursively
def list_files(directory, extensions=None, exclude_prefixes=('.',)):
    if type(extensions) == str:
        extensions = [extensions]
    if extensions is not None:
        extensions = [('' if e.startswith('.') else '.') + e for e in extensions]
    for root, dirnames, filenames in os.walk(directory):
        filenames = [f for f in filenames if not f.startswith(exclude_prefixes)]
        dirnames[:] = [d for d in dirnames if not d.startswith(exclude_prefixes)]
        for filename in filenames:
            base, ext = os.path.splitext(filename)
            joined = os.path.join(root, filename)
            if extensions is None or ext.lower() in extensions:
                yield joined
                
def get_stem(fn):
    return os.path.splitext(os.path.basename(fn))[0]