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author | Raymond Hettinger <python@rcn.com> | 2009-04-10 19:02:36 (GMT) |
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committer | Raymond Hettinger <python@rcn.com> | 2009-04-10 19:02:36 (GMT) |
commit | 5bfd8ce56fc03cf40f192df8651b3d98259f889a (patch) | |
tree | b11640e7c186c0079995c5b06b6454b82ee473e4 /Doc/library/itertools.rst | |
parent | c2a4f4fb67a76cb04731beebc515878f9b91674c (diff) | |
download | cpython-5bfd8ce56fc03cf40f192df8651b3d98259f889a.zip cpython-5bfd8ce56fc03cf40f192df8651b3d98259f889a.tar.gz cpython-5bfd8ce56fc03cf40f192df8651b3d98259f889a.tar.bz2 |
Add examples.
Diffstat (limited to 'Doc/library/itertools.rst')
-rw-r--r-- | Doc/library/itertools.rst | 79 |
1 files changed, 21 insertions, 58 deletions
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst index 68ce02c..9f6f2f6 100644 --- a/Doc/library/itertools.rst +++ b/Doc/library/itertools.rst @@ -34,30 +34,30 @@ operator can be mapped across two vectors to form an efficient dot-product: **Infinite Iterators:** - ================== ================= ================================================= - Iterator Arguments Results - ================== ================= ================================================= - :func:`count` start, [step] start, start+step, start+2*step, ... - :func:`cycle` p p0, p1, ... plast, p0, p1, ... - :func:`repeat` elem [,n] elem, elem, elem, ... endlessly or up to n times - ================== ================= ================================================= +================== ================= ================================================= ========================================= +Iterator Arguments Results Example +================== ================= ================================================= ========================================= +:func:`count` start, [step] start, start+step, start+2*step, ... ``count(10) --> 10 11 12 13 14 ...`` +:func:`cycle` p p0, p1, ... plast, p0, p1, ... ``cycle('ABCD') --> A B C D A B C D ...`` +:func:`repeat` elem [,n] elem, elem, elem, ... endlessly or up to n times ``repeat(10, 3) --> 10 10 10`` +================== ================= ================================================= ========================================= **Iterators terminating on the shortest input sequence:** - ==================== ============================ ================================================= - Iterator Arguments Results - ==================== ============================ ================================================= - :func:`chain` p, q, ... p0, p1, ... plast, q0, q1, ... - :func:`compress` data, selectors (d[0] if s[0]), (d[1] if s[1]), ... - :func:`dropwhile` pred, seq seq[n], seq[n+1], starting when pred fails - :func:`filterfalse` pred, seq elements of seq where pred(elem) is False - :func:`groupby` iterable[, keyfunc] sub-iterators grouped by value of keyfunc(v) - :func:`islice` seq, [start,] stop [, step] elements from seq[start:stop:step] - :func:`starmap` func, seq func(\*seq[0]), func(\*seq[1]), ... - :func:`tee` it, n it1, it2 , ... itn splits one iterator into n - :func:`takewhile` pred, seq seq[0], seq[1], until pred fails - :func:`zip_longest` p, q, ... (p[0], q[0]), (p[1], q[1]), ... - ==================== ============================ ================================================= +==================== ============================ ================================================= ============================================================= +Iterator Arguments Results Example +==================== ============================ ================================================= ============================================================= +:func:`chain` p, q, ... p0, p1, ... plast, q0, q1, ... ``chain('ABC', 'DEF') --> A B C D E F`` +: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` pred, seq seq[n], seq[n+1], starting when pred fails ``dropwhile(lambda x: x<5, [1,4,6,4,1]) --> 6 4 1`` +:func:`filterfalse` pred, seq elements of seq where pred(elem) is False ``ifilterfalse(lambda x: x%2, range(10)) --> 0 2 4 6 8`` +:func:`groupby` iterable[, keyfunc] sub-iterators grouped by value of keyfunc(v) +:func:`islice` seq, [start,] stop [, step] elements from seq[start:stop:step] ``islice('ABCDEFG', 2, None) --> C D E F G`` +:func:`starmap` func, seq func(\*seq[0]), func(\*seq[1]), ... ``starmap(pow, [(2,5), (3,2), (10,3)]) --> 32 9 1000`` +:func:`takewhile` pred, seq seq[0], seq[1], until pred fails ``takewhile(lambda x: x<5, [1,4,6,4,1]) --> 1 4`` +:func:`tee` it, n it1, it2 , ... itn splits one iterator into n +:func:`zip_longest` p, q, ... (p[0], q[0]), (p[1], q[1]), ... ``izip_longest('ABCD', 'xy', fillvalue='-') --> Ax By C- D-`` +==================== ============================ ================================================= ============================================================= **Combinatoric generators:** @@ -555,43 +555,6 @@ loops that truncate the stream. *fillvalue* defaults to ``None``. -.. _itertools-example: - -Examples --------- - -The following examples show common uses for each tool and demonstrate ways they -can be combined. - -.. doctest:: - - >>> # Show a dictionary sorted and grouped by value - >>> from operator import itemgetter - >>> d = dict(a=1, b=2, c=1, d=2, e=1, f=2, g=3) - >>> di = sorted(d.items(), key=itemgetter(1)) - >>> for k, g in groupby(di, key=itemgetter(1)): - ... print(k, map(itemgetter(0), g)) - ... - 1 ['a', 'c', 'e'] - 2 ['b', 'd', 'f'] - 3 ['g'] - - >>> # Find runs of consecutive numbers using groupby. The key to the solution - >>> # is differencing with a range so that consecutive numbers all appear in - >>> # same group. - >>> data = [ 1, 4,5,6, 10, 15,16,17,18, 22, 25,26,27,28] - >>> for k, g in groupby(enumerate(data), lambda t:t[0]-t[1]): - ... print(map(operator.itemgetter(1), g)) - ... - [1] - [4, 5, 6] - [10] - [15, 16, 17, 18] - [22] - [25, 26, 27, 28] - - - .. _itertools-recipes: Recipes |