python exec函数创建实例_python内建eval, exec 和exec函数的用法

函数原型：

eval(str [,globals [,locals ]])

可以用来将字符串str当成有效Python表达式来求值，并返回计算结果。同样地, exec语句将字符串str当成有效Python代码来执行。最后，execfile(filename [,globals [,locals ]])函数可以用来执行一个文件。

例如：现在有一个字符串,形如字典值dict值，需要把它转换成python 的 dict 数据，我们可以用eval()函数来转换，代码如下

"{

'Define1':[[63.3,0.00,0.5,0.3,0.0],[269.3,0.034,1.0,1.0,0.5],[332.2,0.933,0.2,0.99920654296875,1],[935.0,0.990,0.2,0.1,1.0]],

'Define2':[[63.3,0.00,0.5,0.2,1.0],[269.3,0.034,1.0,0.3,0.5],[332.2,0.933,0.2, 0.4,0.6],[935.0,0.990,1.0, 0.5,0.0]],

}"

#-------------------------------------------------------------------------------#Name: 模块1#Purpose:#

#Author: User#

#Created: 11/10/2012#Copyright: (c) User 2012#Licence: #-------------------------------------------------------------------------------

defmain():

dictString= "{'Define1':[[63.3,0.00,0.5,0.3,0.0],[269.3,0.034,1.0,1.0,0.5],[332.2,0.933,0.2,0.99920654296875,1],[935.0,0.990,0.2,0.1,1.0]],'Define2':[[63.3,0.00,0.5,0.2,1.0],[269.3,0.034,1.0,0.3,0.5],[332.2,0.933,0.2, 0.4,0.6],[935.0,0.990,1.0, 0.5,0.0]],}"dict=eval(dictString)print "keys:", dict.keys()print "Define1 value", dict['Define1']if __name__ == '__main__':

main()