manually open context manager

Question

My question is, how can I execute any context manager without using with?

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Python has the idea of context managers,

instead of

Answer 1

You can still use with syntax in the interactive console, however a context is based on 2 magic methods __enter__ and __exit__, so you can just use them:

class MyCtx(object):
  def __init__(self, f):
    self.f = f

  def __enter__(self):
    print("Enter")
    return self.f

  def __exit__(*args, **kwargs):
    print("Exit")

def foo():
  print("Hello")

usually you do:

with MyCtx(foo) as f:
  f()

Same as:

ctx = MyCtx(foo)
f = ctx.__enter__()
f() 
ctx.__exit__()

Here you have the live example

Remember that contexts __exit__ method are used for managing errors within the context, so most of them have a signature of __exit__(exception_type, exception_value, traceback), if you dont need to handle it for the tests, just give it some None values:

__exit__(None, None, None)