Backport documentation improvements.

This commit is contained in:
Raymond Hettinger 2008-03-07 20:08:41 +00:00
parent 3662c9090d
commit 94a7036f1f
1 changed files with 39 additions and 32 deletions

View File

@ -68,6 +68,7 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def chain(*iterables):
# chain('ABC', 'DEF') --> A B C D E F
for it in iterables:
for element in it:
yield element
@ -83,6 +84,7 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def count(n=0):
# count(10) --> 10 11 12 13 14 ...
while True:
yield n
n += 1
@ -100,6 +102,7 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def cycle(iterable):
# cycle('ABCD') --> A B C D A B C D A B C D ...
saved = []
for element in iterable:
yield element
@ -121,6 +124,7 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def dropwhile(predicate, iterable):
# dropwhile(lambda x: x<5, [1,4,6,4,1]) --> 6 4 1
iterable = iter(iterable)
for x in iterable:
if not predicate(x):
@ -156,6 +160,8 @@ by functions or loops that truncate the stream.
\begin{verbatim}
class groupby(object):
# [k for k, g in groupby('AAAABBBCCDAABBB')] --> A B C D A B
# [(list(g)) for k, g in groupby('AAAABBBCCD')] --> AAAA BBB CC D
def __init__(self, iterable, key=None):
if key is None:
key = lambda x: x
@ -187,6 +193,7 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def ifilter(predicate, iterable):
# ifilter(lambda x: x%2, range(10)) --> 1 3 5 7 9
if predicate is None:
predicate = bool
for x in iterable:
@ -203,6 +210,7 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def ifilterfalse(predicate, iterable):
# ifilterfalse(lambda x: x%2, range(10)) --> 0 2 4 6 8
if predicate is None:
predicate = bool
for x in iterable:
@ -225,6 +233,7 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def imap(function, *iterables):
# imap(pow, (2,3,10), (5,2,3)) --> 32 9 1000
iterables = map(iter, iterables)
while True:
args = [i.next() for i in iterables]
@ -251,6 +260,10 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def islice(iterable, *args):
# islice('ABCDEFG', 2) --> A B
# islice('ABCDEFG', 2, 4) --> C D
# islice('ABCDEFG', 2, None) --> C D E F G
# islice('ABCDEFG', 0, None, 2) --> A C E G
s = slice(*args)
it = iter(xrange(s.start or 0, s.stop or sys.maxint, s.step or 1))
nexti = it.next()
@ -274,6 +287,7 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def izip(*iterables):
# izip('ABCD', 'xy') --> Ax By
iterables = map(iter, iterables)
while iterables:
result = [it.next() for it in iterables]
@ -311,6 +325,7 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def repeat(object, times=None):
# repeat(10, 3) --> 10 10 10
if times is None:
while True:
yield object
@ -331,6 +346,7 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def starmap(function, iterable):
# starmap(pow, [(2,5), (3,2), (10,3)]) --> 32 9 1000
iterable = iter(iterable)
while True:
yield function(*iterable.next())
@ -343,6 +359,7 @@ by functions or loops that truncate the stream.
\begin{verbatim}
def takewhile(predicate, iterable):
# takewhile(lambda x: x<5, [1,4,6,4,1]) --> 1 4
for x in iterable:
if predicate(x):
yield x
@ -389,34 +406,6 @@ demonstrate ways they can be combined.
\begin{verbatim}
>>> amounts = [120.15, 764.05, 823.14]
>>> for checknum, amount in izip(count(1200), amounts):
... print 'Check %d is for $%.2f' % (checknum, amount)
...
Check 1200 is for $120.15
Check 1201 is for $764.05
Check 1202 is for $823.14
>>> import operator
>>> for cube in imap(operator.pow, xrange(1,5), repeat(3)):
... print cube
...
1
8
27
64
>>> reportlines = ['EuroPython', 'Roster', '', 'alex', '', 'laura',
'', 'martin', '', 'walter', '', 'mark']
>>> for name in islice(reportlines, 3, None, 2):
... print name.title()
...
Alex
Laura
Martin
Walter
Mark
# 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)
@ -529,10 +518,8 @@ def repeatfunc(func, times=None, *args):
def pairwise(iterable):
"s -> (s0,s1), (s1,s2), (s2, s3), ..."
a, b = tee(iterable)
try:
b.next()
except StopIteration:
pass
for elem in b:
break
return izip(a, b)
def grouper(n, iterable, padvalue=None):
@ -543,4 +530,24 @@ def reverse_map(d):
"Return a new dict with swapped keys and values"
return dict(izip(d.itervalues(), d))
def roundrobin(*iterables):
"roundrobin('abc', 'd', 'ef') --> 'a', 'd', 'e', 'b', 'f', 'c'"
# Recipe credited to George Sakkis
pending = len(iterables)
nexts = cycle(iter(it).next for it in iterables)
while pending:
try:
for next in nexts:
yield next()
except StopIteration:
pending -= 1
nexts = cycle(islice(nexts, pending))
def powerset(iterable):
"powerset('ab') --> set([]), set(['a']), set(['b']), set(['a', 'b'])"
# Recipe credited to Eric Raymond
pairs = [(2**i, x) for i, x in enumerate(iterable)]
for n in xrange(2**len(pairs)):
yield set(x for m, x in pairs if m&n)
\end{verbatim}