See this issue: https://bugs.python.org/issue31299
On Saturday, May 29, 2021, 07:19:32 PM GMT+1, André Roberge
<[email protected]> wrote:
With CPython, tracebacks obtained from code written in C can be extremely
clean compared with functionally equivalent code written in Python. Consider
the following test file where I am using a local copy of Python's datetime.py
module.
```pyfrom local_datetime import date
d = date(2021, 13, 1)
```
Executing this code results in the following, very "clean"
traceback:```pytbTraceback (most recent call last):
File "test.py", line 2, in <module>
d = date(2021, 13, 1)
ValueError: month must be in 1..12
```
A single line of code is shown, which is the one written by the end-user of
this library; all code details from inside the library module are hidden.
As it turns out, the datetime module imports (if it is available) the _datetime
module written in C. If we comment out this import, so that the pure Python
code is used instead,here is the new traceback:
```pytbTraceback (most recent call last):
File "test.py", line 2, in <module>
d = date(2021, 13, 1)
File "C:\Users\andre\local_datetime.py", line 847, in __new__
year, month, day = _check_date_fields(year, month, day)
File "C:\Users\andre\local_datetime.py", line 422, in _check_date_fields
raise ValueError('month must be in 1..12', month)
ValueError: ('month must be in 1..12', 13)
```
In addition to the call by the end-user of that library, we see some inner code
of that library that has no practical value to the end-user.
We can suppress some lines of the traceback by replacing the line
```pyyear, month, day = _check_date_fields(year, month, day)
```by```pytry:
year, month, day = _check_date_fields(year, month, day)
except Exception:
_, _, tb = sys.exc_info()
tb.tb_next = None
raise
```
which simplifies the traceback somewhat:```pytbTraceback (most recent call
last):
File "test.py", line 2, in <module>
d = date(2021, 13, 1)
File "C:\Users\andre\local_datetime.py", line 848, in __new__
year, month, day = _check_date_fields(year, month, day)
ValueError: ('month must be in 1..12', 13)
```but there is still one line of code from inside the library.===Idea: it
would be nice if one could somehow define **callables** with a custom attribute
thatwould indicate that tracebacks should not include frames "below" it.More
explicitly, using the notation of the above example, imagine that we could write
```pydate.__hide_tb__ = True```and that any call to `date()` that generate a
traceback would not show frames below thecalling frame, thus reproducing what
we see when using the C code in this example.For library writers, this would be
easily reverted when attempting to debug.For end users, this would result in
much more readable tracebacks, unencumbered by extra lines of code that are
outside of their control.
André Roberge
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