New submission from Victor Porton <por...@narod.ru>:
argparse produces a long unreadable, non-understandable for non-programmers
error message when a subparser is not specified in the command line.
Note that the below message contains Ubuntu specifics, but it seems it would be
nearly as unclear on other OSes too.
The worst thing about this error message is that to produce something readable
instead I need to somehow parse the command string (or at least to catch
TypeError).
$ python3.7 test.py
Traceback (most recent call last):
File "test.py", line 10, in <module>
args = parser.parse_args()
File "/usr/lib/python3.7/argparse.py", line 1754, in parse_args
args, argv = self.parse_known_args(args, namespace)
File "/usr/lib/python3.7/argparse.py", line 1786, in parse_known_args
namespace, args = self._parse_known_args(args, namespace)
File "/usr/lib/python3.7/argparse.py", line 2021, in _parse_known_args
', '.join(required_actions))
TypeError: sequence item 0: expected str instance, NoneType found
Error in sys.excepthook:
Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/apport_python_hook.py", line 63, in
apport_excepthook
from apport.fileutils import likely_packaged, get_recent_crashes
File "/usr/lib/python3/dist-packages/apport/__init__.py", line 5, in <module>
from apport.report import Report
File "/usr/lib/python3/dist-packages/apport/report.py", line 30, in <module>
import apport.fileutils
File "/usr/lib/python3/dist-packages/apport/fileutils.py", line 23, in
<module>
from apport.packaging_impl import impl as packaging
File "/usr/lib/python3/dist-packages/apport/packaging_impl.py", line 24, in
<module>
import apt
File "/usr/lib/python3/dist-packages/apt/__init__.py", line 23, in <module>
import apt_pkg
ModuleNotFoundError: No module named 'apt_pkg'
Original exception was:
Traceback (most recent call last):
File "test.py", line 10, in <module>
args = parser.parse_args()
File "/usr/lib/python3.7/argparse.py", line 1754, in parse_args
args, argv = self.parse_known_args(args, namespace)
File "/usr/lib/python3.7/argparse.py", line 1786, in parse_known_args
namespace, args = self._parse_known_args(args, namespace)
File "/usr/lib/python3.7/argparse.py", line 2021, in _parse_known_args
', '.join(required_actions))
TypeError: sequence item 0: expected str instance, NoneType found
The script follows.
#!/usr/bin/env python
import argparse
parser = argparse.ArgumentParser(description="Automatically process XML")
subparsers = parser.add_subparsers(title='subcommands')
chain_parser = subparsers.add_parser('chain', aliases=['c'],
help='Automatically run a chain of transformations')
args = parser.parse_args()
----------
components: Library (Lib)
messages: 322164
nosy: porton
priority: normal
severity: normal
status: open
title: argparse: Missing subparser error message should be more clear
type: behavior
versions: Python 3.7
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue34191>
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