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bpo-30538: Update count() in Functional Programming HOWTO #1919

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bpo-30538: Update count() in Functional Programming HOWTO #1919

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bpo-30538: Update count() in Functional HOWTO
csabella Jun 2, 2017
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bpo-30538: Update enumerate() arguments in Functional HOWTO
csabella Jun 3, 2017
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23 changes: 14 additions & 9 deletions Doc/howto/functional.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -653,8 +653,9 @@ This can also be written as a list comprehension:
[0, 2, 4, 6, 8]


:func:`enumerate(iter) <enumerate>` counts off the elements in the iterable,
returning 2-tuples containing the count and each element. ::
:func:`enumerate(iter, start=0) <enumerate>` counts off the elements in the
iterable returning 2-tuples containing the count (from *start*) and
each element. ::

>>> for item in enumerate(['subject', 'verb', 'object']):
... print(item)
Expand Down Expand Up @@ -747,14 +748,16 @@ The module's functions fall into a few broad classes:
Creating new iterators
----------------------

:func:`itertools.count(n) <itertools.count>` returns an infinite stream of
integers, increasing by 1 each time. You can optionally supply the starting
number, which defaults to 0::
:func:`itertools.count(start, step) <itertools.count>` returns an infinite
stream of evenly spaced values. You can optionally supply the starting number,
which defaults to 0, and the interval between numbers, which defaults to 1::

itertools.count() =>
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, ...
itertools.count(10) =>
10, 11, 12, 13, 14, 15, 16, 17, 18, 19, ...
itertools.count(10, 5) =>
10, 15, 20, 25, 30, 35, 40, 45, 50, 55, ...

:func:`itertools.cycle(iter) <itertools.cycle>` saves a copy of the contents of
a provided iterable and returns a new iterator that returns its elements from
Expand Down Expand Up @@ -1060,10 +1063,10 @@ write the obvious :keyword:`for` loop::
for i in [1,2,3]:
product *= i

A related function is `itertools.accumulate(iterable, func=operator.add) <itertools.accumulate`.
It performs the same calculation, but instead of returning only the
final result, :func:`accumulate` returns an iterator that also yields
each partial result::
A related function is :func:`itertools.accumulate(iterable, func=operator.add)
<itertools.accumulate>`. It performs the same calculation, but instead of
returning only the final result, :func:`accumulate` returns an iterator that
also yields each partial result::

itertools.accumulate([1,2,3,4,5]) =>
1, 3, 6, 10, 15
Expand Down Expand Up @@ -1235,6 +1238,8 @@ Python documentation

Documentation for the :mod:`itertools` module.

Documentation for the :mod:`functools` module.

Documentation for the :mod:`operator` module.

:pep:`289`: "Generator Expressions"
Expand Down