From 2e155536caf8a090c06d62dd92647abc62362463 Mon Sep 17 00:00:00 2001 From: Raymond Hettinger Date: Fri, 27 Sep 2024 11:43:46 -0700 Subject: Itertool docs: Minor clarifications, wording tweaks, spacing, and active voice. (gh-124690) Minor clarifications, wording tweaks, spacing, and active voice. --- Doc/library/itertools.rst | 34 +++++++++++++++++++++------------- 1 file changed, 21 insertions(+), 13 deletions(-) diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst index c1299eb..9a62249 100644 --- a/Doc/library/itertools.rst +++ b/Doc/library/itertools.rst @@ -58,7 +58,7 @@ Iterator Arguments Results :func:`compress` data, selectors (d[0] if s[0]), (d[1] if s[1]), ... ``compress('ABCDEF', [1,0,1,0,1,1]) → A C E F`` :func:`dropwhile` predicate, seq seq[n], seq[n+1], starting when predicate fails ``dropwhile(lambda x: x<5, [1,4,6,3,8]) → 6 3 8`` :func:`filterfalse` predicate, seq elements of seq where predicate(elem) fails ``filterfalse(lambda x: x<5, [1,4,6,3,8]) → 6 8`` -:func:`groupby` iterable[, key] sub-iterators grouped by value of key(v) ``groupby(['A','B','ABC'], len) → (1, A B) (3, ABC)`` +:func:`groupby` iterable[, key] sub-iterators grouped by value of key(v) ``groupby(['A','B','DEF'], len) → (1, A B) (3, DEF)`` :func:`islice` seq, [start,] stop [, step] elements from seq[start:stop:step] ``islice('ABCDEFG', 2, None) → C D E F G`` :func:`pairwise` iterable (p[0], p[1]), (p[1], p[2]) ``pairwise('ABCDEFG') → AB BC CD DE EF FG`` :func:`starmap` func, seq func(\*seq[0]), func(\*seq[1]), ... ``starmap(pow, [(2,5), (3,2), (10,3)]) → 32 9 1000`` @@ -93,7 +93,7 @@ Examples Results Itertool Functions ------------------ -The following module functions all construct and return iterators. Some provide +The following functions all construct and return iterators. Some provide streams of infinite length, so they should only be accessed by functions or loops that truncate the stream. @@ -131,11 +131,12 @@ loops that truncate the stream. total = function(total, element) yield total - The *function* argument can be set to :func:`min` for a running - minimum, :func:`max` for a running maximum, or :func:`operator.mul` - for a running product. `Amortization tables - `_ - can be built by accumulating interest and applying payments: + To compute a running minimum, set *function* to :func:`min`. + For a running maximum, set *function* to :func:`max`. + Or for a running product, set *function* to :func:`operator.mul`. + To build an `Amortization table + `_, + accumulate the interest and apply payments: .. doctest:: @@ -202,10 +203,10 @@ loops that truncate the stream. .. function:: chain(*iterables) - Make an iterator that returns elements from the first iterable until it is - exhausted, then proceeds to the next iterable, until all of the iterables are - exhausted. Used for treating consecutive sequences as a single sequence. - Roughly equivalent to:: + Make an iterator that returns elements from the first iterable until + it is exhausted, then proceeds to the next iterable, until all of the + iterables are exhausted. This combines multiple data sources into a + single iterator. Roughly equivalent to:: def chain(*iterables): # chain('ABC', 'DEF') → A B C D E F @@ -353,10 +354,12 @@ loops that truncate the stream. def cycle(iterable): # cycle('ABCD') → A B C D A B C D A B C D ... + saved = [] for element in iterable: yield element saved.append(element) + while saved: for element in saved: yield element @@ -396,8 +399,10 @@ loops that truncate the stream. def filterfalse(predicate, iterable): # filterfalse(lambda x: x<5, [1,4,6,3,8]) → 6 8 + if predicate is None: predicate = bool + for x in iterable: if not predicate(x): yield x @@ -474,7 +479,7 @@ loops that truncate the stream. If *start* is zero or ``None``, iteration starts at zero. Otherwise, elements from the iterable are skipped until *start* is reached. - If *stop* is ``None``, iteration continues until the iterable is + If *stop* is ``None``, iteration continues until the input is exhausted, if at all. Otherwise, it stops at the specified position. If *step* is ``None``, the step defaults to one. Elements are returned @@ -520,8 +525,10 @@ loops that truncate the stream. def pairwise(iterable): # pairwise('ABCDEFG') → AB BC CD DE EF FG + iterator = iter(iterable) a = next(iterator, None) + for b in iterator: yield a, b a = b @@ -584,7 +591,8 @@ loops that truncate the stream. .. function:: product(*iterables, repeat=1) - Cartesian product of input iterables. + `Cartesian product `_ + of the input iterables. Roughly equivalent to nested for-loops in a generator expression. For example, ``product(A, B)`` returns the same as ``((x,y) for x in A for y in B)``. -- cgit v0.12