[docs] [issue29981] Update Index set, dict, and generator 'comprehensions'

[Terry J. Reedy]

New submission from Terry J. Reedy:

The index currently has

comprehensions
   *list*

with *list* linked to 6.2.5 List displays.  I suggest:

1. Link *comprehensions* to 6.2.4. Displays for lists, sets and dictionaries
2. Add subentries *set*, *dict*, and *generator* linked to
2a. 6.2.6. Set displays
2b. 6.2.7. Dictionary displays
2c. 6.2.8. Generator expressions

We don't *call* generator expressions 'generator comprehensions', but that is what they are syntactically and one looking for 'comprehensions' should be able to find them there.

There is already

*list*
   ...
   *comprehensions*
   ...
*list comprehensions*

with 'list' and 'list comprehensions' linked to glossary entries, while 'list, comprehensions' links to the same section as 'comprehensions, list'.  

3. Add 'set/dictionary, comprehensions' sub-entries linked like 'list, com
4. Add Glossary entries and links like 'list comprehensions'

----------
assignee: docs at python
components: Documentation
keywords: easy
messages: 291129
nosy: docs at python, terry.reedy
priority: normal
severity: normal
stage: needs patch
status: open
title: Update Index set, dict, and generator 'comprehensions'
type: behavior
versions: Python 3.6, Python 3.7

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue29981>
_______________________________________