[Python-Dev] Re: Reviving PEP 473

March 16, 2021

      I am not a Python developer, but I am very interested in this topic.  While I would definitely make use of any additional fields for exceptions as discussed, it is already possible to find most, if not all of the information discussed in PEP 473. To give just a concrete example taken from the PEP:
```
Friendly Console version 0.3.1. [Python version: 3.8.4]
...
...
...
a = {'foo': 1}
a['fo']
Traceback (most recent call last):
  File "<friendly-console:2>", line 1, in <module>
    a['fo']
KeyError: 'fo'

Did you mean foo?
...
...
...
foo = 1
fo
Traceback (most recent call last):
  File "<friendly-console:5>", line 1, in <module>
    fo
NameError: name 'fo' is not defined

Did you mean foo?
...
...
...
The above two examples are the actual output done by a program I work on called friendly (formerly known as friendly-traceback) and are essentially identical to what is given in PEP 473 as a desired outcome. 

Much information about IndexError, AttributeError, etc, mentioned as desirable in PEP 473 can already be obtained by such automated tools.  Using friendly as an example, a sample of what's possible can be found  at https://aroberge.github.io/friendly-traceback-docs/docs/html/tracebacks_en_3.8.html

Of course, having information more easily available about specific exceptions would be welcome and make it easier and likely more error-proof to write automated tools.  But since much of the information is already available (if one looks hard enough...), the cost of adding fields to existing exceptions should be carefully evaluated.

André Roberge