[issue33049] itertools.count() confusingly mentions zip() and sequence numbers

[Raymond Hettinger]

Raymond Hettinger  added the comment:

Since I don't like "sequential numbers", let's opt for the "leave it alone" 
option :-)

--
resolution:  -> not a bug
stage:  -> resolved
status: open -> closed

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[issue33049] itertools.count() confusingly mentions zip() and sequence numbers

[Terry J. Reedy]

Terry J. Reedy  added the comment:

I think 'sequential numbers' would be slightly better than 'sequence numbers'.  
To be, it better includes stepped and descending sequences.  (Enough better 
that I would be willing to do the PR and merge.)  Otherwise, I think leave it 
alone.

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nosy: +terry.reedy
versions:  -Python 3.4, Python 3.5

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[issue33049] itertools.count() confusingly mentions zip() and sequence numbers

[Raymond Hettinger]

Raymond Hettinger  added the comment:

> This is a strange thing to note though because enumerate 
> would be a better use here.

IIRC, the wording predates the addition of enumerate() and before enumerate() 
grew a *start* argument.  That said, enumerate() just addresses care the most 
common case.  It is still worth mentioning that count() is still useful for the 
general case of adding sequence numbers to data streams woven together by zip() 
-- like the way auto-increment is used in SQL:

from time import ctime

def timestamp():
while True:
yield ctime()
   
def user_request():
while True:
yield input()
 
logged_requests = zip(user_request(), count(1), timestamp(), 
cycle(available_servers))

> it seems like step should instead be mentioned there
> instead of "sequence numbers".

The *step* argument was a late addition to the API and isn't used much in 
practice.  When it is used, its meaning and use case tend to be self-evident 
(i.e. counting 60 seconds at a time, or counting backwards), so it doesn't 
warrant further elaboration.

The sentence as-is is imperfect (it makes you wonder why not just use 
enumerate) but it seems better than either saying less by not mentioning the 
use case or getting too wordy which would place too much emphasis on use cases 
less common that those served by enumerate().  So, my preference is to leave 
the sentence as it stands.  The intent of the two sentences mentioning map() 
and zip() was to hint at the possibilities while still keeping the paragraph 
primary focused on what count() actually does.

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assignee: docs@python -> rhettinger
priority: normal -> low

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[issue33049] itertools.count() confusingly mentions zip() and sequence numbers

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

For example zip(my_sequence, count(1)).

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nosy: +rhettinger, serhiy.storchaka

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[issue33049] itertools.count() confusingly mentions zip() and sequence numbers

[Trey Hunner]

New submission from Trey Hunner :

>From the itertools documentation: 
>https://docs.python.org/3/library/itertools.html?highlight=itertools#itertools.count

> Also, used with zip() to add sequence numbers.

I'm not certain what the goal of the original sentence was, but I think it's 
unclear as currently written.

I assume this is what's meant:

my_sequence = [1, 2, 3, 4]
for i, item in zip(count(1), my_sequence):
print(i, item)

This is a strange thing to note though because enumerate would be a better use 
here.

my_sequence = [1, 2, 3, 4]
for i, item in enumerate(my_sequence, start=1):
print(i, item)

Maybe what is meant is that count can be used with a step while enumerate 
cannot?

my_sequence = [1, 2, 3, 4]
for i, item in zip(count(step=5), my_sequence):
print(i, item)

If that's the case it seems like step should instead be mentioned there instead 
of "sequence numbers".

--
assignee: docs@python
components: Documentation
messages: 313606
nosy: docs@python, trey
priority: normal
severity: normal
status: open
title: itertools.count() confusingly mentions zip() and sequence numbers
type: enhancement
versions: Python 2.7, Python 3.4, Python 3.5, Python 3.6, Python 3.7, Python 3.8

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