Created
August 2, 2017 08:06
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Conditional "with" context manager
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""" | |
Python3 conditional locking example | |
""" | |
from threading import Lock | |
lock = Lock() | |
class ConditionalLock(object): | |
"""silly example to test locking via context manager""" | |
def __init__(self, lockrequest=True, verbose=False): | |
self.lockrequest = lockrequest | |
self.verbose = verbose | |
def __enter__(self): | |
if self.lockrequest: | |
if self.verbose: | |
print("I'd better be locking, then.") | |
lock.acquire() | |
if self.verbose: | |
print("Success: Lock acquired!") | |
else: | |
if self.verbose: | |
print("I will do no locking") | |
def __exit__(self, exc_type, exc_value, traceback): | |
if self.lockrequest: | |
if self.verbose: | |
print("Unlocking attempt in progress.") | |
lock.release() | |
if self.verbose: | |
print("Success. The lock is history.") | |
else: | |
if self.verbose: | |
print("No need to do any unlocking") | |
if __name__ == '__main__': | |
with ConditionalLock(lockrequest=False, verbose=True): | |
print('I am working!') | |
with ConditionalLock(lockrequest=True, verbose=True): | |
print('I am working with a lock!') | |
try: | |
raise RuntimeError('Ooops!') | |
except RuntimeError as e: | |
print('I think I saw a runtime error') | |
raise |
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