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Minor updates:

Browse source 
* Updated comment on design of imap()
* Added untraversed object in izip() structure
* Replaced the pairwise() example with a more general window() example
This commit is contained in:
Raymond Hettinger 2003-06-18 19:25:37 +00:00
parent 3a8fbe7eec
commit befa37dd05
3 changed files with 38 additions and 12 deletions
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15
Doc/lib/libitertools.tex
View file

@ -358,10 +358,6 @@ from building blocks.
... "Returns True if pred(x) is False for every element in the iterable"
... return not nth(ifilter(pred, seq), 0)
>>> def pairwise(seq):
... "s -> (s0,s1), (s1,s2), (s2, s3), ..."
... return izip(seq, islice(seq,1,None))
>>> def padnone(seq):
... "Returns the sequence elements and then returns None indefinitely"
... return chain(seq, repeat(None))
@ -373,4 +369,15 @@ from building blocks.
>>> def dotproduct(vec1, vec2):
... return sum(imap(operator.mul, vec1, vec2))
>>> def window(seq, n=2):
... "Returns a sliding window (of width n) over data from the iterable"
... " s -> (s0,s1,...s[n-1]), (s1,s2,...,sn), ... "
... it = iter(seq)
... result = tuple(islice(it, n))
... if len(result) == n:
... yield result
... for elem in it:
... result = result[1:] + (elem,)
... yield result
\end{verbatim}

19
Lib/test/test_itertools.py
View file

@ -427,10 +427,6 @@ Samuele
... "Returns True if pred(x) is False for every element in the iterable"
... return not nth(ifilter(pred, seq), 0)
>>> def pairwise(seq):
... "s -> (s0,s1), (s1,s2), (s2, s3), ..."
... return izip(seq, islice(seq,1,len(seq)))
>>> def padnone(seq):
... "Returns the sequence elements and then returns None indefinitely"
... return chain(seq, repeat(None))
@ -442,6 +438,16 @@ Samuele
>>> def dotproduct(vec1, vec2):
... return sum(imap(operator.mul, vec1, vec2))
>>> def window(seq, n=2):
... "Returns a sliding window (of width n) over data from the iterable"
... " s -> (s0,s1,...s[n-1]), (s1,s2,...,sn), ... "
... it = iter(seq)
... result = tuple(islice(it, n))
... if len(result) == n:
... yield result
... for elem in it:
... result = result[1:] + (elem,)
... yield result
This is not part of the examples but it tests to make sure the definitions
perform as purported.
@ -473,9 +479,12 @@ True
>>> no(lambda x: x%2==0, [1, 2, 5, 9])
False
>>> list(pairwise('abc'))
>>> list(window('abc'))
[('a', 'b'), ('b', 'c')]
>>> list(window('abc',5))
[]
>>> list(islice(padnone('abc'), 0, 6))
['a', 'b', 'c', None, None, None]

16
Modules/itertoolsmodule.c
View file

@ -882,7 +882,7 @@ the following reasons:
None.
4) If a need does arise, it can be met by __builtins__.map() or by
writing a generator.
writing: chain(iterable, repeat(None)).
5) Similar toolsets in Haskell and SML do not have automatic None fill-in.
*/
@ -1574,8 +1574,18 @@ izip_dealloc(izipobject *lz)
static int
izip_traverse(izipobject *lz, visitproc visit, void *arg)
{
if (lz->ittuple)
return visit(lz->ittuple, arg);
int err;
if (lz->ittuple) {
err = visit(lz->ittuple, arg);
if (err)
return err;
}
if (lz->result) {
err = visit(lz->result, arg);
if (err)
return err;
}
return 0;
}