[Python-checkins] r79482 - python/branches/release26-maint/Doc/library/itertools.rst
raymond.hettinger
python-checkins at python.org
Sun Mar 28 20:12:35 CEST 2010
Author: raymond.hettinger
Date: Sun Mar 28 20:12:35 2010
New Revision: 79482
Log:
Update itertools recipes.
Modified:
python/branches/release26-maint/Doc/library/itertools.rst
Modified: python/branches/release26-maint/Doc/library/itertools.rst
==============================================================================
--- python/branches/release26-maint/Doc/library/itertools.rst (original)
+++ python/branches/release26-maint/Doc/library/itertools.rst Sun Mar 28 20:12:35 2010
@@ -632,9 +632,6 @@
"Return first n items of the iterable as a list"
return list(islice(iterable, n))
- def enumerate(iterable, start=0):
- return izip(count(start), iterable)
-
def tabulate(function, start=0):
"Return function(0), function(1), ..."
return imap(function, count(start))
@@ -741,10 +738,9 @@
seen = set()
seen_add = seen.add
if key is None:
- for element in iterable:
- if element not in seen:
- seen_add(element)
- yield element
+ for element in ifilterfalse(seen.__contains__, iterable):
+ seen_add(element)
+ yield element
else:
for element in iterable:
k = key(element)
@@ -758,6 +754,30 @@
# unique_justseen('ABBCcAD', str.lower) --> A B C A D
return imap(next, imap(itemgetter(1), groupby(iterable, key)))
+ def iter_except(func, exception, first=None):
+ """ Call a function repeatedly until an exception is raised.
+
+ Converts a call-until-exception interface to an iterator interface.
+ Like __builtin__.iter(func, sentinel) but uses an exception instead
+ of a sentinel to end the loop.
+
+ Examples:
+ bsddbiter = iter_except(db.next, bsddb.error, db.first)
+ heapiter = iter_except(functools.partial(heappop, h), IndexError)
+ dictiter = iter_except(d.popitem, KeyError)
+ dequeiter = iter_except(d.popleft, IndexError)
+ queueiter = iter_except(q.get_nowait, Queue.Empty)
+ setiter = iter_except(s.pop, KeyError)
+
+ """
+ try:
+ if first is not None:
+ yield first()
+ while 1:
+ yield func()
+ except exception:
+ pass
+
Note, many of the above recipes can be optimized by replacing global lookups
with local variables defined as default values. For example, the
*dotproduct* recipe can be written as::
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