patch contextmanager

gistfile1.txt

# file foo.py

def zack():
    return "zack
    
# file patcher.py

class Patch1:
    def __init__(self, object, patch):
        self.object = object
        self.patch = patch

    def __enter__(self):
        self.pre_patch_value = object
        self.object = self.patch
        
    def __exit__(self, exc_type, exc_value, traceback):
        self.object = self.pre_patch_value
        
        
class Patch2:
    def __init__(self, object, name, patch):
        self.object = object
        self.name = name
        self.patch = patch
        
    def __enter__(self):
        self.pre_patch_value = getattr(self.object, self.name)
        setattr(self.object, self.name, self.patch)
        
    def __exit__(self, exc_type, exc_value, traceback):
        setattr(self.object, self.name, self.pre_patch_value)
        
# file bar.py

import patcher
import foo

with patcher.Patch1(foo.zack, lambda: "bumm"):
    print(foo.zack())  # this prints "zack"
    
with patcher.Patch2(foo, "zack", lambda: "bumm"):
    print(foo.zack())   # this print "bumm"