How to imitate Python 3's raise ... from in Python 2?

Question

Python 3 has the neat

try:     raise OneException('sorry') except OneException as e:     # after a failed attempt of mitigation:     raise AnotherException('I give up') from e 

syntax which allows raising a followup exception without loosing context. The best analogy I could come up with in Python 2 is

raise AnotherException((e,'I give up')), None, sys.exc_info()[2] 

where the (e,'') is an ugly hack to have the original exception's name included in the message. But isn't there a better way?

Answer 1

There's a raise_from in python-future; simply install it

pip install future 

and import to use

from future.utils import raise_from # or: from six import reraise as raise_from  class FileDatabase:     def __init__(self, filename):         try:             self.file = open(filename)         except IOError as exc:             raise_from(DatabaseError('failed to open'), exc) 

UPDATE

The compatibility package six also supports raise_from, from version 1.9 (released in 2015). It is used in the same manner as above.