mirror of https://github.com/python/cpython
Add examples.
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Raymond Hettinger
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@ -36,49 +36,49 @@ operator can be mapped across two vectors to form an efficient dot-product:
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**Infinite Iterators:**
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**Infinite Iterators:**
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================== ================= =================================================
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================== ================= ================================================= =========================================
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Iterator Arguments Results
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Iterator Arguments Results Example
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================== ================= =================================================
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================== ================= ================================================= =========================================
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:func:`count` start, [step] start, start+step, start+2*step, ...
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:func:`count` start, [step] start, start+step, start+2*step, ... ``count(10) --> 10 11 12 13 14 ...``
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:func:`cycle` p p0, p1, ... plast, p0, p1, ...
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:func:`cycle` p p0, p1, ... plast, p0, p1, ... ``cycle('ABCD') --> A B C D A B C D ...``
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:func:`repeat` elem [,n] elem, elem, elem, ... endlessly or up to n times
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:func:`repeat` elem [,n] elem, elem, elem, ... endlessly or up to n times ``repeat(10, 3) --> 10 10 10``
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================== ================= =================================================
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================== ================= ================================================= =========================================
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**Iterators terminating on the shortest input sequence:**
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**Iterators terminating on the shortest input sequence:**
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==================== ============================ =================================================
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==================== ============================ ================================================= =============================================================
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Iterator Arguments Results
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Iterator Arguments Results Example
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==================== ============================ =================================================
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==================== ============================ ================================================= =============================================================
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:func:`chain` p, q, ... p0, p1, ... plast, q0, q1, ...
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:func:`chain` p, q, ... p0, p1, ... plast, q0, q1, ... ``chain('ABC', 'DEF') --> A B C D E F``
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:func:`compress` data, selectors (d[0] if s[0]), (d[1] if s[1]), ...
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: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``
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:func:`dropwhile` pred, seq seq[n], seq[n+1], starting when pred fails
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:func:`dropwhile` pred, seq seq[n], seq[n+1], starting when pred fails ``dropwhile(lambda x: x<5, [1,4,6,4,1]) --> 6 4 1``
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:func:`groupby` iterable[, keyfunc] sub-iterators grouped by value of keyfunc(v)
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:func:`groupby` iterable[, keyfunc] sub-iterators grouped by value of keyfunc(v)
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:func:`ifilter` pred, seq elements of seq where pred(elem) is True
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:func:`ifilter` pred, seq elements of seq where pred(elem) is True ``ifilter(lambda x: x%2, range(10)) --> 1 3 5 7 9``
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:func:`ifilterfalse` pred, seq elements of seq where pred(elem) is False
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:func:`ifilterfalse` pred, seq elements of seq where pred(elem) is False ``ifilterfalse(lambda x: x%2, range(10)) --> 0 2 4 6 8``
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:func:`islice` seq, [start,] stop [, step] elements from seq[start:stop:step]
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:func:`islice` seq, [start,] stop [, step] elements from seq[start:stop:step] ``islice('ABCDEFG', 2, None) --> C D E F G``
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:func:`imap` func, p, q, ... func(p0, q0), func(p1, q1), ...
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:func:`imap` func, p, q, ... func(p0, q0), func(p1, q1), ... ``imap(pow, (2,3,10), (5,2,3)) --> 32 9 1000``
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:func:`starmap` func, seq func(\*seq[0]), func(\*seq[1]), ...
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:func:`starmap` func, seq func(\*seq[0]), func(\*seq[1]), ... ``starmap(pow, [(2,5), (3,2), (10,3)]) --> 32 9 1000``
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:func:`tee` it, n it1, it2 , ... itn splits one iterator into n
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:func:`tee` it, n it1, it2 , ... itn splits one iterator into n
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:func:`takewhile` pred, seq seq[0], seq[1], until pred fails
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:func:`takewhile` pred, seq seq[0], seq[1], until pred fails ``takewhile(lambda x: x<5, [1,4,6,4,1]) --> 1 4``
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:func:`izip` p, q, ... (p[0], q[0]), (p[1], q[1]), ...
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:func:`izip` p, q, ... (p[0], q[0]), (p[1], q[1]), ... ``izip('ABCD', 'xy') --> Ax By``
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:func:`izip_longest` p, q, ... (p[0], q[0]), (p[1], q[1]), ...
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:func:`izip_longest` p, q, ... (p[0], q[0]), (p[1], q[1]), ... ``izip_longest('ABCD', 'xy', fillvalue='-') --> Ax By C- D-``
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==================== ============================ =================================================
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==================== ============================ ================================================= =============================================================
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**Combinatoric generators:**
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**Combinatoric generators:**
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============================================== ==================== =============================================================
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============================================== ==================== =============================================================
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Iterator Arguments Results
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Iterator Arguments Results
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============================================== ==================== =============================================================
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============================================== ==================== =============================================================
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:func:`product` p, q, ... [repeat=1] cartesian product, equivalent to a nested for-loop
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:func:`product` p, q, ... [repeat=1] cartesian product, equivalent to a nested for-loop
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:func:`permutations` p[, r] r-length tuples, all possible orderings, no repeated elements
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:func:`permutations` p[, r] r-length tuples, all possible orderings, no repeated elements
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:func:`combinations` p[, r] r-length tuples, in sorted order, no repeated elements
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:func:`combinations` p[, r] r-length tuples, in sorted order, no repeated elements
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:func:`combinations_with_replacement` p[, r] r-length tuples, in sorted order, with repeated elements
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:func:`combinations_with_replacement` p[, r] r-length tuples, in sorted order, with repeated elements
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``product('ABCD', repeat=2)`` ``AA AB AC AD BA BB BC BD CA CB CC CD DA DB DC DD``
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``product('ABCD', repeat=2)`` ``AA AB AC AD BA BB BC BD CA CB CC CD DA DB DC DD``
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``permutations('ABCD', 2)`` ``AB AC AD BA BC BD CA CB CD DA DB DC``
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``permutations('ABCD', 2)`` ``AB AC AD BA BC BD CA CB CD DA DB DC``
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``combinations('ABCD', 2)`` ``AB AC AD BC BD CD``
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``combinations('ABCD', 2)`` ``AB AC AD BC BD CD``
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``combinations_with_replacement('ABCD', 2)`` ``AA AB AC AD BB BC BD CC CD DD``
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``combinations_with_replacement('ABCD', 2)`` ``AA AB AC AD BB BC BD CC CD DD``
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============================================== ==================== =============================================================
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============================================== ==================== =============================================================
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.. _itertools-functions:
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.. _itertools-functions:
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@ -641,43 +641,6 @@ loops that truncate the stream.
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.. versionadded:: 2.4
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.. versionadded:: 2.4
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.. _itertools-example:
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Examples
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--------
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The following examples show common uses for each tool and demonstrate ways they
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can be combined.
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.. doctest::
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>>> # Show a dictionary sorted and grouped by value
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>>> from operator import itemgetter
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>>> d = dict(a=1, b=2, c=1, d=2, e=1, f=2, g=3)
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>>> di = sorted(d.iteritems(), key=itemgetter(1))
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>>> for k, g in groupby(di, key=itemgetter(1)):
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... print k, map(itemgetter(0), g)
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...
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1 ['a', 'c', 'e']
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2 ['b', 'd', 'f']
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3 ['g']
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>>> # Find runs of consecutive numbers using groupby. The key to the solution
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>>> # is differencing with a range so that consecutive numbers all appear in
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>>> # same group.
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>>> data = [ 1, 4,5,6, 10, 15,16,17,18, 22, 25,26,27,28]
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>>> for k, g in groupby(enumerate(data), lambda (i,x):i-x):
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... print map(itemgetter(1), g)
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...
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[1]
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[4, 5, 6]
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[10]
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[15, 16, 17, 18]
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[22]
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[25, 26, 27, 28]
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.. _itertools-recipes:
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.. _itertools-recipes:
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Recipes
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Recipes
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