Mock implementation using context manager

context_manager.py

import mock

class Patchee(object):
    def name(self):
        return "Patchee"
class MyContextPatcher(object):
    def __init__(self, newName):
        self.newName = newName

    def __enter__(self):
        self.patcher = mock.patch.object(Patchee, 'name', return_value=self.newName)
        self.patcher.start()
        return self
    
    def __exit__(self, *args, **kwargs):
        self.patcher.stop()

with MyContextPatcher('Apatchee') as p:
    # This shall return mocked value Apatchee
    print Patchee().name()
# This shall return the original value Patchee
print Patchee().name()

exception_in_context.py

#Below is a sample of operation flow with exceptions in context manager.
class ExceptionRaiserContext(object):
    def __init__(self, raiseException ):
        self.raiseException = raiseException

    def __enter__(self):
        print "Enter called"
        if self.raiseException:
            raise Exception("Exception raised in enter")

    def __exit__(self, exc_type, exc_val, exc_tb):
        print "Exit called with exception", exc_type

#Example of no exception ( All blocks are executed )
with ExceptionRaiserContext(False):
    print "Operation performed"
#Example of exception at __enter__ ( Enter executed till exception )
with ExceptionRaiserContext(True):
    print "Operation performed"
#Example of exception at operation ( All blocks are executed )
with ExceptionRaiserContext(False):
    print "Operation performed"
    raise Exception("Exception raised in operation")

file_read_in_context.py

# 1.
myFile = open('test.txt')
print myFile.read()

# 2. 
with open('test.txt') as myFile:
	print myFile.read()