Hi,
Any new scope entered or exited could be traced by defining a custom
tracing function and setting it using the sys
<https://docs.python.org/3/library/sys.html> module through sys.settrace()
<https://docs.python.org/3/library/sys.html#sys.settrace> or
sys.setprofile() <https://docs.python.org/3/library/sys.html#sys.setprofile>.
This is also true for multithreaded applications using the threading
<https://docs.python.org/3/library/threading.html> module.
Thus, it is rather vague whether the __enter__() and __exit__() functions
executed by a with statement could be traced, and if so, in what cases. For
instance, _thread.LockType or simply primitive lock objects from
threading being
used with the context management (i.e. with statement) might not allow us
to trace a lock being acquired or released. In other words whether the
__enter__() function that calls acquire() is called. After some
experimentation, unfortunately this is not the case if either Python or C
functions (for CPython) are traced.
So the question whether with-statements could be traced by the python
interpreter ought to be clearly stated since in some cases it works and in
some doesn't.
_____________________________________________________________________________
*EXAMPLE:*
import threading
import sys
def tracer(frame, event, arg):
if event == 'call':
print(f"Entering: {frame.f_code.co_name}")
return tracer
elif event == 'c_call':
print(f"C --- Entering: {arg.__name__}")
elif event == 'return':
print(f"Returning: {arg!r}")
elif event == 'c_return':
print(f"C --- Returning from: {arg.__name__}")
lock = threading.Lock()
sys.setprofile(tracer)
threading.setprofile(tracer)
print("Begin...")
# In the following case, we would see the C functions
# being called: acquire and release
lock.acquire()
print("Do some routine with explicit locking")
lock.release()
print("In the middle...")
# In the following case, we cannot see that any locking is happening,
# nor if the __enter__() and __exit__() methods called
with lock:
print("Do some routine with locking using context management")
print("End...")
_______________________________________________________________________________________
Best,
Mohamad
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