python中的str()与eval函数

author：headsen chen  

date：2018-04-09   10:48:22

eval函数是把str转化成list、dict、tuple

str函数把list，dict，tuple转为为字符串

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# 字符串转换成列表
a = "[[1,2], [3,4], [5,6], [7,8], [9,0]]"
print(type(a))
b = eval(a)
print(b,type(b))

<class 'str'>
([1, 2], [3, 4], [5, 6], [7, 8], [9, 0]) <class 'tuple'>

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# 字符串转换成字典

a = "{1: 'a', 2: 'b'}"
print(type(a))
b = eval(a)
print(b,type(b))

<class 'str'>
{1: 'a', 2: 'b'} <class 'dict'>

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# 字符串转换成元组
a = "([1,2], [3,4], [5,6], [7,8], (9,0))"
print(type(a))
b=eval(a)
print(b,type(b))

<class 'str'>
([1, 2], [3, 4], [5, 6], [7, 8], [9, 0]) <class 'tuple'>