Issue 25926: Clarify that the pure python equivalents are only approximate.
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Raymond Hettinger
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5f7110304c
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672866d009
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@ -97,7 +97,7 @@ loops that truncate the stream.
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:class:`~fractions.Fraction`.) If the input iterable is empty, the
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output iterable will also be empty.
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Equivalent to::
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Roughly equivalent to::
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def accumulate(iterable, func=operator.add):
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'Return running totals'
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@ -156,7 +156,7 @@ loops that truncate the stream.
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Make an iterator that returns elements from the first iterable until it is
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exhausted, then proceeds to the next iterable, until all of the iterables are
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exhausted. Used for treating consecutive sequences as a single sequence.
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Equivalent to::
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Roughly equivalent to::
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def chain(*iterables):
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# chain('ABC', 'DEF') --> A B C D E F
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@ -189,7 +189,7 @@ loops that truncate the stream.
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value. So if the input elements are unique, there will be no repeat
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values in each combination.
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Equivalent to::
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Roughly equivalent to::
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def combinations(iterable, r):
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# combinations('ABCD', 2) --> AB AC AD BC BD CD
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@ -238,7 +238,7 @@ loops that truncate the stream.
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value. So if the input elements are unique, the generated combinations
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will also be unique.
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Equivalent to::
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Roughly equivalent to::
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def combinations_with_replacement(iterable, r):
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# combinations_with_replacement('ABC', 2) --> AA AB AC BB BC CC
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@ -278,7 +278,7 @@ loops that truncate the stream.
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Make an iterator that filters elements from *data* returning only those that
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have a corresponding element in *selectors* that evaluates to ``True``.
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Stops when either the *data* or *selectors* iterables has been exhausted.
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Equivalent to::
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Roughly equivalent to::
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def compress(data, selectors):
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# compress('ABCDEF', [1,0,1,0,1,1]) --> A C E F
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@ -291,7 +291,7 @@ loops that truncate the stream.
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Make an iterator that returns evenly spaced values starting with number *start*. Often
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used as an argument to :func:`map` to generate consecutive data points.
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Also, used with :func:`zip` to add sequence numbers. Equivalent to::
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Also, used with :func:`zip` to add sequence numbers. Roughly equivalent to::
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def count(start=0, step=1):
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# count(10) --> 10 11 12 13 14 ...
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@ -312,7 +312,7 @@ loops that truncate the stream.
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Make an iterator returning elements from the iterable and saving a copy of each.
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When the iterable is exhausted, return elements from the saved copy. Repeats
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indefinitely. Equivalent to::
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indefinitely. Roughly equivalent to::
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def cycle(iterable):
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# cycle('ABCD') --> A B C D A B C D A B C D ...
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@ -333,7 +333,7 @@ loops that truncate the stream.
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Make an iterator that drops elements from the iterable as long as the predicate
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is true; afterwards, returns every element. Note, the iterator does not produce
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*any* output until the predicate first becomes false, so it may have a lengthy
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start-up time. Equivalent to::
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start-up time. Roughly equivalent to::
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def dropwhile(predicate, iterable):
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# dropwhile(lambda x: x<5, [1,4,6,4,1]) --> 6 4 1
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@ -349,7 +349,7 @@ loops that truncate the stream.
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Make an iterator that filters elements from iterable returning only those for
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which the predicate is ``False``. If *predicate* is ``None``, return the items
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that are false. Equivalent to::
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that are false. Roughly equivalent to::
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def filterfalse(predicate, iterable):
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# filterfalse(lambda x: x%2, range(10)) --> 0 2 4 6 8
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@ -386,7 +386,7 @@ loops that truncate the stream.
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groups.append(list(g)) # Store group iterator as a list
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uniquekeys.append(k)
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:func:`groupby` is equivalent to::
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:func:`groupby` is roughly equivalent to::
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class groupby:
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# [k for k, g in groupby('AAAABBBCCDAABBB')] --> A B C D A B
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@ -426,7 +426,7 @@ loops that truncate the stream.
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specified position. Unlike regular slicing, :func:`islice` does not support
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negative values for *start*, *stop*, or *step*. Can be used to extract related
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fields from data where the internal structure has been flattened (for example, a
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multi-line report may list a name field on every third line). Equivalent to::
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multi-line report may list a name field on every third line). Roughly equivalent to::
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def islice(iterable, *args):
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# islice('ABCDEFG', 2) --> A B
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@ -464,7 +464,7 @@ loops that truncate the stream.
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value. So if the input elements are unique, there will be no repeat
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values in each permutation.
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Equivalent to::
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Roughly equivalent to::
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def permutations(iterable, r=None):
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# permutations('ABCD', 2) --> AB AC AD BA BC BD CA CB CD DA DB DC
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@ -510,7 +510,7 @@ loops that truncate the stream.
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Cartesian product of input iterables.
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Equivalent to nested for-loops in a generator expression. For example,
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Roughly equivalent to nested for-loops in a generator expression. For example,
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``product(A, B)`` returns the same as ``((x,y) for x in A for y in B)``.
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The nested loops cycle like an odometer with the rightmost element advancing
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@ -522,7 +522,7 @@ loops that truncate the stream.
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repetitions with the optional *repeat* keyword argument. For example,
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``product(A, repeat=4)`` means the same as ``product(A, A, A, A)``.
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This function is equivalent to the following code, except that the
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This function is roughly equivalent to the following code, except that the
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actual implementation does not build up intermediate results in memory::
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def product(*args, repeat=1):
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@ -541,7 +541,9 @@ loops that truncate the stream.
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Make an iterator that returns *object* over and over again. Runs indefinitely
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unless the *times* argument is specified. Used as argument to :func:`map` for
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invariant parameters to the called function. Also used with :func:`zip` to
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create an invariant part of a tuple record. Equivalent to::
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create an invariant part of a tuple record.
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Roughly equivalent to::
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def repeat(object, times=None):
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# repeat(10, 3) --> 10 10 10
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@ -564,7 +566,7 @@ loops that truncate the stream.
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the iterable. Used instead of :func:`map` when argument parameters are already
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grouped in tuples from a single iterable (the data has been "pre-zipped"). The
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difference between :func:`map` and :func:`starmap` parallels the distinction
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between ``function(a,b)`` and ``function(*c)``. Equivalent to::
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between ``function(a,b)`` and ``function(*c)``. Roughly equivalent to::
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def starmap(function, iterable):
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# starmap(pow, [(2,5), (3,2), (10,3)]) --> 32 9 1000
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@ -575,7 +577,7 @@ loops that truncate the stream.
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.. function:: takewhile(predicate, iterable)
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Make an iterator that returns elements from the iterable as long as the
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predicate is true. Equivalent to::
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predicate is true. Roughly equivalent to::
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def takewhile(predicate, iterable):
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# takewhile(lambda x: x<5, [1,4,6,4,1]) --> 1 4
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@ -592,7 +594,9 @@ loops that truncate the stream.
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The following Python code helps explain what *tee* does (although the actual
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implementation is more complex and uses only a single underlying
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:abbr:`FIFO (first-in, first-out)` queue)::
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:abbr:`FIFO (first-in, first-out)` queue).
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Roughly equivalent to::
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def tee(iterable, n=2):
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it = iter(iterable)
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@ -623,7 +627,7 @@ loops that truncate the stream.
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Make an iterator that aggregates elements from each of the iterables. If the
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iterables are of uneven length, missing values are filled-in with *fillvalue*.
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Iteration continues until the longest iterable is exhausted. Equivalent to::
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Iteration continues until the longest iterable is exhausted. Roughly equivalent to::
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class ZipExhausted(Exception):
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pass
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