from __future__ import absolute_import
from threading import local
class TransactionContext(object):
def __init__(self, stack, context):
self.stack = stack
self.context = context
def __enter__(self):
self.stack.push(self.context)
return self
def __exit__(self, *exc_info):
self.stack.pop(self.context)
class TransactionStack(local):
def __init__(self):
self.stack = []
def __len__(self):
return len(self.stack)
def __iter__(self):
return iter(self.stack)
def __call__(self, context):
return TransactionContext(self, context)
def clear(self):
self.stack = []
def peek(self):
try:
return self.stack[-1]
except IndexError:
return None
def push(self, context):
self.stack.append(context)
return context
def pop(self, context=None):
if context is None:
return self.stack.pop()
while self.stack:
if self.stack.pop() is context:
return context
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