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python映射列表实例分析

WBOY
Release： 2016-06-10 15:18:07
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本文实例讲述了python映射列表。分享给大家供大家参考。具体分析如下：

列表映射是个非常有用的方法，通过对列表的每个元素应用一个函数来转换数据，可以使用一种策略或者方法来遍历计算每个元素。

例如：

复制代码 代码如下:
params = {"server":"mpilgrim", \
                "database":"master", \
                "uid":"sa", \
                "pwd":"secret" \
                }
print ["%s=%s" % (k, params[k]) for k in params.keys()]
print ';'.join(["%s=%s" % (k, params[k]) for k in params.keys()])

返回结果为：

复制代码 代码如下:
['uid=sa', 'pwd=secret', 'database=master', 'server=mpilgrim']
 
还可以改进下，把元组转化成字符串，使用join函数方法。
复制代码 代码如下:
'uid=sa;pwd=secret;database=master;server=mpilgrim'
(join函数不仅使用于元组还使用于列表，功能是字符串化）
split跟join相反，把字符串转换成元组
看如下应用
复制代码 代码如下:
str = 'server=mpilgrim;uid=sa;database=master;pwd=secret'>>> str.split(';')
['server=mpilgrim', 'uid=sa', 'database=master', 'pwd=secret']
>>> str.split(';', 1)
['server=mpilgrim', 'uid=sa;database=master;pwd=secret']
>>> str.split(';', 2)
['server=mpilgrim', 'uid=sa', 'database=master;pwd=secret']

列表映射用例：

复制代码 代码如下:
>>>> li = [1, 9, 8, 4]
>>> [elem*2 for elem in li] 1
[2, 18, 16, 8]
>>> li
[1, 9, 8, 4]

希望本文所述对大家的Python程序设计有所帮助。

Related labels：
python list mapping
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