python迭代器实例简析-Python Tutorial-php.cn

python迭代器实例简析

WBOY

Release： 2016-06-16 08:41:46

Original

1081 people have browsed it

本文实例讲述了python迭代器的简单用法，分享给大家供大家参考。具体分析如下：

生成器表达式是用来生成函数调用时序列参数的一种迭代器写法

生成器对象可以遍历或转化为列表（或元组等数据结构），但不能切片(slicing)。当函数的唯一的实参是可迭代序列时，便可以去掉生成器表达式两端>的圆括号，写出更优雅的代码：

>>>> sum(i for i in xrange(10))
 45

Copy after login

sum声明：

sum(iterable[, start])
Sums start and the items of an iterable from left to right and returns the total. start defaults to 0. The iterable‘s items are normally numbers, and are not allowed to be strings. The fast, correct way to concatenate a sequence of strings is by calling ''.join(sequence). Note that sum(range(n), m) is equivalent to reduce(operator.add, range(n), m) To add floating point values with extended precision, see math.fsum().

参数要求传入可迭代序列，我们传入一个生成器对象，完美实现。

注意区分下面代码：

上面的j为生成器类型，下面的j为list类型:

j = (i for i in range(10)) 
print j,type(j) 
print '*'*70 
 
j = [i for i in range(10)] 
print j,type(j)

Copy after login

结果：

<generator object <genexpr> at 0x01CB1A30> <type 'generator'>
**********************************************************************
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9] <type 'list'>

Copy after login

希望本文所述对大家Python程序设计的学习有所帮助。

Related labels：

python Iterator

source：php.cn

Previous article：python实现通过shelve修改对象实例 Next article：Python中itertools模块用法详解

Statement of this Website

The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn