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Diffstat (limited to 'Doc/library/itertools.rst')
| -rw-r--r-- | Doc/library/itertools.rst | 37 |
1 files changed, 10 insertions, 27 deletions
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst index 368e40d..032c0b8 100644 --- a/Doc/library/itertools.rst +++ b/Doc/library/itertools.rst @@ -22,9 +22,8 @@ The tools are designed to combine readily with one another. This makes it easy to construct more specialized tools succinctly and efficiently in pure Python. For instance, SML provides a tabulation tool: ``tabulate(f)`` which produces a -sequence ``f(0), f(1), ...``. This toolbox provides :func:`imap` and -:func:`count` which can be combined to form ``imap(f, count())`` and produce an -equivalent result. +sequence ``f(0), f(1), ...``. But, this effect can be achieved in Python +by combining :func:`map` and :func:`count` to form ``map(f, count())``. Likewise, the functional tools are designed to work well with the high-speed functions provided by the :mod:`operator` module. @@ -138,7 +137,7 @@ loops that truncate the stream. .. function:: count([n]) Make an iterator that returns consecutive integers starting with *n*. If not - specified *n* defaults to zero. Often used as an argument to :func:`imap` to + specified *n* defaults to zero. Often used as an argument to :func:`map` to generate consecutive data points. Also, used with :func:`izip` to add sequence numbers. Equivalent to:: @@ -248,22 +247,6 @@ loops that truncate the stream. yield x -.. function:: imap(function, *iterables) - - Make an iterator that computes the function using arguments from each of the - iterables. This function is the same as the built-in :func:`map` function. - Equivalent to:: - - def imap(function, *iterables): - iterables = [iter(it) for it in iterables) - while True: - args = [next(it) for it in iterables] - if function is None: - yield tuple(args) - else: - yield function(*args) - - .. function:: islice(iterable, [start,] stop [, step]) Make an iterator that returns selected elements from the iterable. If *start* is @@ -421,7 +404,7 @@ loops that truncate the stream. .. function:: repeat(object[, times]) Make an iterator that returns *object* over and over again. Runs indefinitely - unless the *times* argument is specified. Used as argument to :func:`imap` for + unless the *times* argument is specified. Used as argument to :func:`map` for invariant parameters to the called function. Also used with :func:`izip` to create an invariant part of a tuple record. Equivalent to:: @@ -437,9 +420,9 @@ loops that truncate the stream. .. function:: starmap(function, iterable) Make an iterator that computes the function using arguments obtained from - the iterable. Used instead of :func:`imap` when argument parameters are already + the iterable. Used instead of :func:`map` when argument parameters are already grouped in tuples from a single iterable (the data has been "pre-zipped"). The - difference between :func:`imap` and :func:`starmap` parallels the distinction + difference between :func:`map` and :func:`starmap` parallels the distinction between ``function(a,b)`` and ``function(*c)``. Equivalent to:: def starmap(function, iterable): @@ -507,7 +490,7 @@ can be combined. :: Check 1202 is for $823.14 >>> import operator - >>> for cube in imap(operator.pow, range(1,5), repeat(3)): + >>> for cube in map(operator.pow, range(1,5), repeat(3)): ... print(cube) ... 1 @@ -577,7 +560,7 @@ which incur interpreter overhead. :: def tabulate(function): "Return function(0), function(1), ..." - return imap(function, count()) + return map(function, count()) def nth(iterable, n): "Returns the nth item or raise StopIteration" @@ -603,7 +586,7 @@ which incur interpreter overhead. :: def quantify(seq, pred=None): "Count how many times the predicate is true in the sequence" - return sum(imap(pred, seq)) + return sum(map(pred, seq)) def padnone(seq): """Returns the sequence elements and then returns None indefinitely. @@ -617,7 +600,7 @@ which incur interpreter overhead. :: return chain.from_iterable(repeat(seq, n)) def dotproduct(vec1, vec2): - return sum(imap(operator.mul, vec1, vec2)) + return sum(map(operator.mul, vec1, vec2)) def flatten(listOfLists): return list(chain.from_iterable(listOfLists)) |