python的eval函数作用

>>> eval('pow(2,2)')4

>>> eval('2 + 2')4

>>> eval("n + 4")85

>>> a = "[[1,2], [3,4], [5,6], [7,8], [9,0]]"

>>> b = eval(a)

>>> b

[[1, 2], [3, 4], [5, 6], [7, 8], [9, 0]]

>>> a = "{1:'xx',2:'yy'}"

>>> c = eval(a)

>>> c

{1: 'xx', 2: 'yy'}

>>> a = "(1,2,3,4)"

>>> d = eval(a)

>>> d

(1, 2, 3, 4)

>>> list1 = [1,2,3,4,5]

>>> `list1`

'[1, 2, 3, 4, 5]'

>>> type(`list1`)

<type 'str'>

>>> type(eval(`list1`))

<type 'list'>

>>> a = eval(`list1`)

>>> a

[1, 2, 3, 4, 5]