Python中eval()函数的功能及使用方法小结

>>>a = "[[1,2], [3,4], [5,6], [7,8], [9,0]]"
>>>type(a)
>>> b = eval(a)
>>> print b[[1, 2], [3, 4], [5, 6], [7, 8], [9, 0]]
>>> type(b)

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

>>> a = "([1,2], [3,4], [5,6], [7,8], (9,0))"
>>> type(a)
>>> b = eval(a)
>>> print b([1, 2], [3, 4], [5, 6], [7, 8], (9, 0))
>>> type(b)

>>>a=10;
>>>print(eval("a+1"))
>>>执行结果： 11

>>>a=10;
>>>g={'a':4}
>>>print(eval("a+1",g))
>>>执行结果：5

>>>a=10
>>>b=20
>>>c=30
>>>g={'a':6,'b':8}
>>>t={'b':100,'c':10}
>>>print(eval('a+b+c',g,t))
>>>执行结果：116  （a=6, b=100, c=10）

>>>s='["a","b","c"]'
>>>print(eval(s))
>>>执行结果： ['a', 'b', 'c']

>>>s='abs(-10)'  
>>>print(eval(s))
>>>输出结果：10 

>>>eval("1+2")
>>>执行结果： 3

>>> eval("print(\"hello, world\")")
>>>输出结果：hello, world

>>> 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)

json_string = """{
  "answerList": [
    {
      "content": "string",
      "questionId": "string",
      "questionIndex": 0,
      "questionTitle": "string",
      "questionType": 0,
      "questionWeight": 0,
      "score": 0,
      "scoreId": "string",
      "scoreName": "string",
      "scoreWeight": 0,
      "selectOptions": [
        {
          "disabledWeight": true,
          "evaluateStatus": 0,
          "optionId": "string",
          "optionTitle": "string",
          "optionWeight": 0
        }
      ],
      "tags": [
        {
          "tagId": "string",
          "tagTitle": "string"
        }
      ]
    }
  ],
  "channel": "string",
  "externalUnionid": "string",
  "key": "string",
  "qaJson": "string",
  "unionid": "string",
  "uuid": "string"
}"""
print(json_string) #打印json字符串
print(type(json_string))#打印json字符串的类型：str
print(eval（json_string))使用eval（)表达式把json字符串转换为python数据类型：字典类型--》结果失败，报错
json_dict = json.loads(json_string) #使用json.loads反序列化方式，将json字符串转换为python数据类型成功
print(type(json_dict)) #打印转换后的数据类型：dict
print(json_dict)#打印转换成功后的字典数据

>>> 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]