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17Iterator.py
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17Iterator.py
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#!/usr/bin/python
# coding:utf8
'''
Interator
意图:
提供一种方法顺序访问一个聚合对象中各个元素, 而又不需暴露该对象的内部表示。
适用性:
访问一个聚合对象的内容而无需暴露它的内部表示。
支持对聚合对象的多种遍历。
为遍历不同的聚合结构提供一个统一的接口(即, 支持多态迭代)。
'''
def count_to(count):
"""Counts by word numbers, up to a maximum of five"""
numbers = ["one", "two", "three", "four", "five"]
# enumerate() returns a tuple containing a count (from start which
# defaults to 0) and the values obtained from iterating over sequence
for pos, number in zip(range(count), numbers):
yield number
# Test the generator
count_to_two = lambda: count_to(2)
count_to_five = lambda: count_to(5)
print('Counting to two...')
for number in count_to_two():
print number
print " "
print('Counting to five...')
for number in count_to_five():
print number
print " "