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max_help_position is not works in argparse library #69484
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Hi colleagues I have the code (max_help_position is 2000): formatter_class=lambda prog: argparse.HelpFormatter(prog, max_help_position=2000)
parser = argparse.ArgumentParser(formatter_class=formatter_class)
subparsers = parser.add_subparsers(title="Commands", metavar="<command>")
cmd_parser = subparsers.add_parser('long_long_long_long_long_long_long',
help='- jksljdalkjda',
formatter_class=formatter_class)
args = parser.parse_args(['-h'])
print args Result: we have
instead
The code: class MyFormatter(argparse.HelpFormatter):
def __init__(self, prog):
super(MyFormatter, self).__init__(prog, max_help_position=2000, width=2000)
self._max_help_position = 2000
self._action_max_length += 4 got same result. The strings like: formatter_class = lambda prog: argparse.HelpFormatter(prog,
max_help_position=2000, width=2000)
formatter_class = lambda prog: argparse.HelpFormatter(prog,
max_help_position=1000, width=2000)
formatter_class = lambda prog: argparse.HelpFormatter(prog,
max_help_position=2000, width=1000) got same result: we always have new line after command. |
Problem also described on http://stackoverflow.com/questions/32888815/ |
My testing shows that it's a problem with the subparsers listing. When regular arguments are long, 'max_help_position' works (within limits allowed by 'width'). |
There's a bug in the HelpFormatter.add_argument method. It does not take into account the extra indentation of subactions (sub parsers) when calculating self._action_max_length. The corrected method and a test case is in the attached file. class MyFormatter(argparse.HelpFormatter):
"""
Corrected _max_action_length for the indenting of subactions
"""
def add_argument(self, action):
if action.help is not argparse.SUPPRESS:
# find all invocations
get_invocation = self._format_action_invocation
invocations = [get_invocation(action)]
current_indent = self._current_indent
for subaction in self._iter_indented_subactions(action):
# compensate for the indent that will be added
indent_chg = self._current_indent - current_indent
added_indent = 'x'*indent_chg
invocations.append(added_indent + get_invocation( subaction) )
# print('inv', invocations)
# update the maximum item length
invocation_length = max([len(s) for s in invocations])
action_length = invocation_length + self._current_indent
self._action_max_length = max(self._action_max_length,
action_length)
# add the item to the list
self._add_item(self._format_action, [action]) Without this correction self._action_max_length is off by 2 if a subparser has the longest invocation. Normally that wouldn't be an issue since normally subparser names are short and easy to use. But with the 'aliases' that newer argparse allows, the invocation could be longer, and possibly longer than regular arguments. I haven't passed this correction through test_argparse.py. It also would need a test case or two. I don't think it need a documentation change. I don't know if this correction will work with the subparser grouping proposed in http://bugs.python.org/issue9341. |
The unittest test_argparse.py has one related test class TestAddSubparsers has a long enough subparser invocation (with aliases) to produce wrapping with the default 24 max position:
I don't see anything in the test file that tries to vary the max_help_position parameter. |
Fixed by #124230. |
Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.
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