When I define a function and patch it using the with statement it runs fine. Output: My understanding is that using the with statement would cause the __enter__ and __exit__ methods to be called on the patch object. So I thought that would be equivalent to doing this: The output from the some_func call is the…
Tag: contextmanager
Can we mix contextmanager decorator with __enter__() and __exit__() methods in another class inside the same with statement?
In python3.8 I’m very familiar with the traditional __enter__ and __exit__ magic methods but new to the @contextlib.contextmanager decorator. Is it possible to mix the two patterns inside a single with statement? The following (highly contrived) script should explain the problem more clearly. Is there a…
Conditional or optional context managers in with statement
Suppose I have some kind of context manager (from a third-party library) that I am using like so: But, suppose if there is no value for test_dt, the context manager should not run, but all of the remaining code should run, like so: Assume that lines_of_code here is 2-3 lines of code which are exactly identica…
Why can’t a module be a context manager (to a ‘with’ statement)?
Suppose we have the following mod.py: and the following use of it: I get an error: According to the documentation the documentation the with statement should execute as follows (I believe it fails at step 2 and therefore truncate the list): The context expression (the expression given in the with_item) is eva…
Python How to force object instantiation via Context Manager?
I want to force object instantiation via class context manager. So make it impossible to instantiate directly. I implemented this solution, but technically user can still instantiate object. And context manager: Any better solution ? Answer If you consider that your clients will follow basic python coding pri…
How does pySerial implement the “with” statement without __enter__ and __exit__?
pySerial can be used with Python’s with statement like this: I tried to see exactly what it is pySerial does to make this work, but I couldn’t find an __enter__ or __exit__ function anywhere! I ran grep -e ‘(__enter__)|(__exit__)’ *.py from the pySerial directory, and grep didn’t…