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Kirill Smelkov
cpython
Commits
9e386419
Commit
9e386419
authored
Aug 25, 2003
by
Raymond Hettinger
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Make the derived tools amendable to cut and paste.
parent
9bd308f6
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Doc/lib/libitertools.tex
Doc/lib/libitertools.tex
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Doc/lib/libitertools.tex
View file @
9e386419
...
...
@@ -328,59 +328,59 @@ included here to illustrate how higher level tools can be created
from building blocks.
\begin
{
verbatim
}
>>>
def enumerate
(
iterable
)
:
...
return izip
(
count
()
, iterable
)
>>>
def tabulate
(
function
)
:
...
"Return function
(
0
)
, function
(
1
)
, ..."
...
return imap
(
function, count
())
>>>
def iteritems
(
mapping
)
:
...
return izip
(
mapping.iterkeys
()
, mapping.itervalues
())
>>>
def nth
(
iterable, n
)
:
...
"Returns the nth item"
...
return list
(
islice
(
iterable, n, n
+
1
))
>>>
def all
(
pred, seq
)
:
...
"Returns True if pred
(
x
)
is True for every element in the iterable"
...
return False not in imap
(
pred, seq
)
>>>
def some
(
pred, seq
)
:
...
"Returns True if pred
(
x
)
is True at least one element in the iterable"
...
return True in imap
(
pred, seq
)
>>>
def no
(
pred, seq
)
:
...
"Returns True if pred
(
x
)
is False for every element in the iterable"
...
return True not in imap
(
pred, seq
)
>>>
def quantify
(
pred, seq
)
:
...
"Count how many times the predicate is True in the sequence"
...
return sum
(
imap
(
pred, seq
))
>>>
def padnone
(
seq
)
:
...
"Returns the sequence elements and then returns None indefinitely"
...
return chain
(
seq, repeat
(
None
))
>>>
def ncycles
(
seq, n
)
:
...
"Returns the sequence elements n times"
...
return chain
(*
repeat
(
seq, n
))
>>>
def dotproduct
(
vec
1
, vec
2
)
:
...
return sum
(
imap
(
operator.mul, vec
1
, vec
2
))
>>>
def window
(
seq, n
=
2
)
:
...
"Returns a sliding window
(
of width n
)
over data from the iterable"
...
" s
-
>
(
s
0
,s
1
,...s
[
n
-
1
])
,
(
s
1
,s
2
,...,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
>>>
def take
(
n, seq
)
:
...
return list
(
islice
(
seq, n
))
def enumerate
(
iterable
)
:
return izip
(
count
()
, iterable
)
def tabulate
(
function
)
:
"Return function
(
0
)
, function
(
1
)
, ..."
return imap
(
function, count
())
def iteritems
(
mapping
)
:
return izip
(
mapping.iterkeys
()
, mapping.itervalues
())
def nth
(
iterable, n
)
:
"Returns the nth item"
return list
(
islice
(
iterable, n, n
+
1
))
def all
(
pred, seq
)
:
"Returns True if pred
(
x
)
is True for every element in the iterable"
return False not in imap
(
pred, seq
)
def some
(
pred, seq
)
:
"Returns True if pred
(
x
)
is True at least one element in the iterable"
return True in imap
(
pred, seq
)
def no
(
pred, seq
)
:
"Returns True if pred
(
x
)
is False for every element in the iterable"
return True not in imap
(
pred, seq
)
def quantify
(
pred, seq
)
:
"Count how many times the predicate is True in the sequence"
return sum
(
imap
(
pred, seq
))
def padnone
(
seq
)
:
"Returns the sequence elements and then returns None indefinitely"
return chain
(
seq, repeat
(
None
))
def ncycles
(
seq, n
)
:
"Returns the sequence elements n times"
return chain
(*
repeat
(
seq, n
))
def dotproduct
(
vec
1
, vec
2
)
:
return sum
(
imap
(
operator.mul, vec
1
, vec
2
))
def window
(
seq, n
=
2
)
:
"Returns a sliding window
(
of width n
)
over data from the iterable"
" s
-
>
(
s
0
,s
1
,...s
[
n
-
1
])
,
(
s
1
,s
2
,...,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
def take
(
n, seq
)
:
return list
(
islice
(
seq, n
))
\end
{
verbatim
}
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