python itertools examples

iterstools

#!/usr/bin/env python
# -*- coding: utf-8 -*-

from itertools import *

# imap
for i in imap(lambda x:x*2,xrange(5)):
  print i 
# starmap
values=[(1,2),(5,23),(8,9)]
for i in starmap(lambda x,y:(x,y,x*y),values):
	print i 
# izip
for  i in izip(xrange(1,7),cycle(['a','b','c'])):
	print i 
# repeat
for i in repeat('over-and-over',5):
	print i 
# izip+repeat
for i in izip(count(),repeat('over',6)):
	print i 
# imap+xrange+repeat
for i in imap(lambda x,y:x*y, xrange(5),repeat(2)):
	print i
# chain
for i in chain([1,2,3],['a','b','c']):
	print i 
# izip
for i in izip([1,2,3],['a','b','c']):
	print i 
#islice
for i in islice(count(),5,10,2):
	print i 
# tee
r = izip([1,3,4],[4,5,6])
r1,r2=tee(r)
# 用于部分迭代数据结构
print list(r1)
print list(r2)
#
# dropwhile
# 迭代数据过滤
def f(x):
	print "test:",x
	return (x<1)
for i in [-1,0,1,2]:
	print 'new',i	
	
for i in dropwhile(f,[-1,0,2,3]):
	print i 

#takewhile
# 停止数据处理
for i in takewhile(f,[-1,0,2]):
	print i 
# ifilter
# ifilterfalse
# 数据过滤，处理每一个数据
for i in ifilter(f,[-1,0,2]):
	print "new:tewst",i

class point(object):
	def __init__(self,x,y):
		self.x=x
		self.y=y
	def __repr__(self):
		return '(%s,%s)' % (self.x,self.y)
	def __cmp__(self,other):
		return cmp((self.x,self.y),(other.x,other.y))
data=list(
	imap(
		point,cycle(islice(count(),3)),
		islice(count(),7),
		)
	)
print data 
import pprint
import operator
print pprint.pprint(data)
data.sort()
# groupby 分组
for k,g in groupby(data,operator.attrgetter('x')):
	print k,list(g)

0
2
4
6
8
(1, 2, 2)
(5, 23, 115)
(8, 9, 72)
(1, 'a')
(2, 'b')
(3, 'c')
(4, 'a')
(5, 'b')
(6, 'c')
over-and-over
over-and-over
over-and-over
over-and-over
over-and-over
(0, 'over')
(1, 'over')
(2, 'over')
(3, 'over')
(4, 'over')
(5, 'over')
0
2
4
6
8
1
2
3
a
b
c
(1, 'a')
(2, 'b')
(3, 'c')
5
7
9
[(1, 4), (3, 5), (4, 6)]
[(1, 4), (3, 5), (4, 6)]
new -1
new 0
new 1
new 2
test: -1
test: 0
test: 2
2
3
test: -1
-1
test: 0
0
test: 2
test: -1
new:tewst -1
test: 0
new:tewst 0
test: 2
[(0,0), (1,1), (2,2), (0,3), (1,4), (2,5), (0,6)]
[(0,0), (1,1), (2,2), (0,3), (1,4), (2,5), (0,6)]
None
0 [(0,0), (0,3), (0,6)]
1 [(1,1), (1,4)]
2 [(2,2), (2,5)]
[Finished in 0.1s]