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Code snippet from optparse.py:
 344 self.help_position = min(max_len + 2, self.max_help_position)
 345 self.help_width = self.width - self.help_position
Where self.width is initialized with the COLUMNS environment variable. On narrow terminals it can happen that self.help_position < self.width, leading to an exception in textwrap.py:
 raise ValueError("invalid width %r (must be > 0)" % self.width)
ValueError: invalid width -15 (must be > 0)
A reasonable workaround would be to trim part of the help text instead of causing an exception.

argparse has some similar code in Lib/argparse.py:489. Can you reproduce the problem with argparse?
If you can't and argparse solved the problem already, we might adopt the same solution; if you can, it should be fixed there too.

Yes, argparse has same problem.
>>> import os, argparse
>>> p = argparse.ArgumentParser(prog='PROG')
>>> os.environ['COLUMNS'] = '16'
>>> print(p.format_help())
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "/home/serhiy/py/cpython/Lib/argparse.py", line 2329, in format_help
 return formatter.format_help()
 File "/home/serhiy/py/cpython/Lib/argparse.py", line 276, in format_help
 help = self._root_section.format_help()
 File "/home/serhiy/py/cpython/Lib/argparse.py", line 206, in format_help
 func(*args)
 File "/home/serhiy/py/cpython/Lib/argparse.py", line 206, in format_help
 func(*args)
 File "/home/serhiy/py/cpython/Lib/argparse.py", line 514, in _format_action
 help_lines = self._split_lines(help_text, help_width)
 File "/home/serhiy/py/cpython/Lib/argparse.py", line 614, in _split_lines
 return _textwrap.wrap(text, width)
 File "/home/serhiy/py/cpython/Lib/textwrap.py", line 355, in wrap
 return w.wrap(text)
 File "/home/serhiy/py/cpython/Lib/textwrap.py", line 300, in wrap
 return self._wrap_chunks(chunks)
 File "/home/serhiy/py/cpython/Lib/textwrap.py", line 227, in _wrap_chunks
 raise ValueError("invalid width %r (must be > 0)" % self.width)
ValueError: invalid width 0 (must be > 0)

I think in such case it is reasonable to fail silently, since the information will not be readable anyway.
Is a patch like the attached acceptable? (Sorry, I am new here)
results:
>>> import os, argparse; p = argparse.ArgumentParser(prog='PROG')
>>> os.environ['COLUMNS'] = '0'
>>> print(p.format_help())
usage: PROG
 
 [-h]
optional arguments:
 -h, --help 
>>>

I think "ugly look is better than silence" here. Elazar, can you touch a optparse too (with some tests - test.support.EnvironmentVarGuard context manager will be helpful here)?

> I think "ugly look is better than silence" here.
Agree. We have two possibilities:
1. Decrease an indentation. There is a lot of blank spaces below option's names.
2. Set some minimal width (10 or 20 characters) and let lines wrap out.
For better look we should use both methods.

ok. how about argparse_ugly.patch? below some width it simply won't do any wrapping.
(I hadn't touch optparse yet)

Here is less ugly patch (for argparse and optparse). Instead of prohibiting wrapping at all for small width, it limits minimal width of formatted text. It try first decrease the indent for help.

New changeset 779de7b4909b by Serhiy Storchaka in branch '2.7':
Issue #13107: argparse and optparse no longer raises an exception when output
http://hg.python.org/cpython/rev/779de7b4909b
New changeset c6c30b682e14 by Serhiy Storchaka in branch '3.3':
Issue #13107: argparse and optparse no longer raises an exception when output
http://hg.python.org/cpython/rev/c6c30b682e14
New changeset 48bcd03cd29f by Serhiy Storchaka in branch 'default':
Issue #13107: argparse and optparse no longer raises an exception when output
http://hg.python.org/cpython/rev/48bcd03cd29f 

Thank you Adam for your report. Thank you Elazar for your patch.