import os import sys from contextlib import contextmanager def exists_case_sensitive(path): """ Returns if the given path exists and also matches the case on Windows. When finding files that can be imported, it is important for the cases to match because while file os.path.exists("module.py") and os.path.exists("MODULE.py") both return True on Windows, Python can only import using the case of the real file. """ result = os.path.exists(path) if (sys.platform.startswith('win') or sys.platform == 'darwin') and result: directory, basename = os.path.split(path) result = basename in os.listdir(directory) return result @contextmanager def chdir(path): """Context manager for changing dir and restoring previous workdir after exit. """ curdir = os.getcwd() os.chdir(path) try: yield finally: os.chdir(curdir) def union(a, b): """ Return a list of items that are in `a` or `b` """ u = [] for item in a: if item not in u: u.append(item) for item in b: if item not in u: u.append(item) return u def difference(a, b): """ Return a list of items from `a` that are not in `b`. """ d = [] for item in a: if item not in b: d.append(item) return d