I have been looking into Python's contextmanager (more specifically, Python 3's contextlib or its back ported contextlib2) as of late, and I was wondering what were the advantages/disadvantages writing them as a class vs. a function? They both seem to function the same way and handle exceptions the same way. There's a lot of cool utilities like ExitStack(), but those utilities seem to be implementable in context managers written as classes or functions. Thus, I'm struggling to find a good reason as to why one would want to write context managers verbosely as a class when they can be written as a function and just slap on the contextmanager decorator. Here's a trivial example I wrote to showcase both doing the same thing: # !/usr/bin/python -u # encoding: utf-8 from contextlib import contextmanager # Function-based @contextmanager def func_custom_open(filename, mode): try: f = open(filename, mode) yield f except Exception as e: print(e) finally: f.close() # Class-based class class_custom_open(object): def __init__(self, filename, mode): self.f = open(filename, mode) def __enter__(self): return self.f def __exit__(self, type, value, traceback): self.f.close() if __name__ == '__main__': # Function-based with func_custom_open('holafile_func.txt', 'w') as func_f: func_f.write('hola func!') # Class-based with class_custom_open('holafile_class.txt', 'w') as class_f: class_f.write('hola class!') Continue reading...
