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"""
Providing iterator functions that are not in all version of Python we support.
Where possible, we try to use the system-native version and only fall back to
these implementations if necessary.
"""
import itertools
def compat_tee(iterable):
"""
Return two independent iterators from a single iterable.
Based on http://www.python.org/doc/2.3.5/lib/itertools-example.html
"""
# Note: Using a dictionary and a list as the default arguments here is
# deliberate and safe in this instance.
def gen(next, data={}, cnt=[0]):
dpop = data.pop
for i in itertools.count():
if i == cnt[0]:
item = data[i] = next()
cnt[0] += 1
else:
item = dpop(i)
yield item
next = iter(iterable).next
return gen(next), gen(next)
def groupby(iterable, keyfunc=None):
"""
Taken from http://docs.python.org/lib/itertools-functions.html
"""
if keyfunc is None:
keyfunc = lambda x:x
iterable = iter(iterable)
l = [iterable.next()]
lastkey = keyfunc(l[0])
for item in iterable:
key = keyfunc(item)
if key != lastkey:
yield lastkey, l
lastkey = key
l = [item]
else:
l.append(item)
yield lastkey, l
# Not really in itertools, since it's a builtin in Python 2.4 and later, but it
# does operate as an iterator.
def reversed(data):
for index in xrange(len(data)-1, -1, -1):
yield data[index]
if hasattr(itertools, 'tee'):
tee = itertools.tee
else:
tee = compat_tee
if hasattr(itertools, 'groupby'):
groupby = itertools.groupby
def is_iterable(x):
"A implementation independent way of checking for iterables"
try:
iter(x)
except TypeError:
return False
else:
return True
def sorted(in_value):
"A naive implementation of sorted"
out_value = in_value[:]
out_value.sort()
return out_value
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