Python 2 error in Argparse tutorial

[cf65f861-413d-442f-a4e8-82177d99568a]

BPO	16863
Nosy	@terryjreedy, @ezio-melotti, @bitdancer, @berkerpeksag, @phmc

^{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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GitHub fields: ```python assignee = 'https://github.com/terryjreedy' closed_at = created_at = labels = ['easy', 'type-feature', 'docs'] title = 'Python 2 error in Argparse tutorial' updated_at = user = 'https://bugs.python.org/CharlieDimino' ``` bugs.python.org fields: ```python activity = actor = 'terry.reedy' assignee = 'terry.reedy' closed = True closed_date = closer = 'terry.reedy' components = ['Documentation'] creation = creator = 'Charlie.Dimino' dependencies = [] files = [] hgrepos = [] issue_num = 16863 keywords = ['easy'] message_count = 11.0 messages = ['179041', '179043', '179044', '179045', '179050', '179052', '179108', '179115', '229836', '229837', '229839'] nosy_count = 9.0 nosy_names = ['terry.reedy', 'ezio.melotti', 'r.david.murray', 'docs@python', 'tshepang', 'python-dev', 'berker.peksag', 'pconnell', 'Charlie.Dimino'] pr_nums = [] priority = 'normal' resolution = 'fixed' stage = 'resolved' status = 'closed' superseder = None type = 'enhancement' url = 'https://bugs.python.org/issue16863' versions = ['Python 2.7'] ```

[cf65f861-413d-442f-a4e8-82177d99568a]

http://docs.python.org/2/howto/argparse.html

Error message in the first example is outdated, may indicate further out of date information on page.

Example:

The tutorial says: prog.py: error: the following arguments are required: echo

When the actual error received is: prog.py: error: too few arguments

[bitdancer]

Actually it looks like it is future-dated. The documented error message is the one you get from 3.3. I guess someone backported a doc change for a feature change.

[bitdancer]

Ah, the whole tutorial is newish. So this is a bug just in the 2.7 version of the tutorial (it doesn't match the 2.7 code), and yes, there may be other issues as well.

[bitdancer]

See bpo-14034. Ezio apparently left the error messages unchanged on purpose...I'm not sure why.

[ezio-melotti]

When I backported the patch I probably didn't want to try all the examples to see what the py2 error was. In addition the py3 error is more clear even if it doesn't match what you actually get. I think this can be closed as won't fix, unless someone wants to propose a patch.

[cf65f861-413d-442f-a4e8-82177d99568a]

If it's okay, don't close this just yet. I'm new to this system but I'll submit a patch with any fixes to the tutorial I find.

[terryjreedy]

A quick patch would be 'This tutorial was written for argparse in Python 3. A few details are different in 2.x.' But feel free to do better.

[ccda776a-4736-4dbd-bf35-88e58f6952ba]

A quick patch would be 'This tutorial was written for argparse in Python 3. A few details are different in 2.x.' But feel free to do better.

That really sounds great, especially since it avoids resorting to things as ugly as "...and this is Python 2 output".

[terryjreedy]

Since the author of the tutorial agrees with my idea, and no one has come forward with anything else, I will make the change.

[1762cc99-3127-4a62-9baf-30c3d0f51ef7]

New changeset e7428d7f641f by Terry Jan Reedy in branch '2.7': Issue bpo-16863: Explain difference between text and 2.7 behavior. https://hg.python.org/cpython/rev/e7428d7f641f

[terryjreedy]

Once this discrepancy is explained (3.x) prog.py: error: the following arguments are required: echo (2.7) prog.py: error: too few arguments I agree with leaving the 3.x version in the tutorial. A normal output discrepany might be a different matter.