Some useful decorators and classes for Python

decorators.py

# (c) Stefan Countryman 2017
# useful classes and decorators for Python code, particularly python 2.7

def multiprocessing_traceback(func):
    """A decorator for formatting exception traceback into a string to aid in
    debugging when using the ``multiprocessing`` module."""
    import traceback, functools
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        try:
            return func(*args, **kwargs)
        except Exception as e:
            msg = "{}\n\nOriginal {}".format(e, traceback.format_exc())
            raise type(e)(msg)
    return wrapper

class Cacheable(object):
    """An object that can store the output of property getter functions in a
    "private" cache to avoid regeneration times. The cache can be flushed if
    data needs to be regenerated from sources."""
    @staticmethod
    def _cacheable(property_func):
        """A decorator that makes an object property cacheable, i.e. the
        function generating the data will not be called if the data has
        already been generated. This can be cancelled by flushing cache."""
        def wrapper(self, *args, **kwargs):
            if not hasattr(self, '_cache'):
                setattr(self, '_cache', dict())
            prop_key = str(hash(property_func))
            if not self._cache.has_key(prop_key):
                self._cache[prop_key] = property_func(self, *args, **kwargs)
            return self._cache[prop_key]
        return wrapper
    def _clear_cache(obj):
        """Delete the _cache property used by the @_cacheable decorator (if
        present)."""
        if hasattr(obj, '_cache'):
            delattr('_cache')