Python Conditional “With” Lock Design

Question

I am trying to do some shared locking using with statements

def someMethod(self, hasLock = False):
     with self.my_lock:
         self.somethingElse(hasLoc         


        

Answer 1

The Python or is short circuiting so you can make the locking conditional:

def somethingElse(self, hasLock = False):
    #I want this to be conditional...
    with hasLock or self.my_lock:
          print 'i hate hello worlds'

Unfortunately it's not quite that easy, because a boolean isn't a valid return from a with statement. You'll need to create a class with the __enter__ and __exit__ to wrap the boolean True value.

Here's one possible implementation that I haven't tested.

from contextlib import contextmanager

@contextmanager
def withTrue():
    yield True

def withbool(condition):
    if condition:
        return withTrue()
    return False

def somethingElse(self, hasLock = False):
    with withbool(hasLock) or self.my_lock():
          print 'i hate hello worlds'

This is a lot of boilerplate for something so simple, so the RLock solution looks like a winner. This solution might be useful in a different context though.