New submission from Andrew Barnert:

A PyStructSequence type doesn't expose its field names in any way to Python 
code (except indirectly, via the repr, which you could parse if you really 
wanted to…).

The docs claim that "Struct sequence objects are the C equivalent of 
namedtuple() objects", so it seems like the obvious way to expose them is the 
exact same way namedtuple types do—as a class attribute named "_fields".

Also, in #7796, and in a recent thread on python-ideas, multiple people 
suggested that "named tuple" is a protocol, not a type, and duck typing on 
_fields is the obvious way to detect types matching that protocol.

Only the "sequence fields" need to be exposed—fields that don't match up to 
sequence indices aren't named tuple fields, they're just extra instance 
attributes (that don't even show up in the repr).

Patch included. For the tests, I tested the fields in struct_time and 
stat_result in effectively the same way test_repr tests their repr, so it 
should pass on all the same platforms/builds.

----------
files: structseq.diff
keywords: patch
messages: 207991
nosy: abarnert
priority: normal
severity: normal
status: open
title: structseq types should expose _fields
type: enhancement
Added file: http://bugs.python.org/file33436/structseq.diff

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<http://bugs.python.org/issue20230>
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