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:     <your licence>
#-------------------------------------------------------------------------------


def main():
    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()