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import sys
from collections import deque
class nested(object):
def __init__(self, *contexts):
self.contexts = contexts
self.entered = None
def __context__(self):
return self
def __enter__(self):
if self.entered is not None:
raise RuntimeError("Context is not reentrant")
self.entered = deque()
vars = []
try:
for context in self.contexts:
mgr = context.__context__()
vars.append(mgr.__enter__())
self.entered.appendleft(mgr)
except:
self.__exit__(*sys.exc_info())
raise
return vars
def __exit__(self, *exc_info):
# Behave like nested with statements
# first in, last out
# New exceptions override old ones
ex = exc_info
for mgr in self.entered:
try:
mgr.__exit__(*ex)
except:
ex = sys.exc_info()
self.entered = None
if ex is not exc_info:
raise ex[0], ex[1], ex[2]
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