r = {'is_claimed': 'True', 'rating': 3.5}
r = json.dumps(r)
file.write(str(r['rating']))
我无法访问 JSON 中的数据。我做错了什么？
TypeError: string indices must be integers, not str
【问题讨论】：
标签： python json python-2.7 dictionary
json.dumps() 返回 python dict 的 JSON 字符串表示。 See the docs
你不能这样做 r['rating'] 因为 r 是一个字符串，而不是一个字典
也许你的意思是这样的
r = {'is_claimed': 'True', 'rating': 3.5}
json = json.dumps(r) # note i gave it a different name
file.write(str(r['rating']))
【讨论】：
无需使用json.dumps()将其转换为字符串
r = {'is_claimed': 'True', 'rating': 3.5}
file.write(r['is_claimed'])
file.write(str(r['rating']))
您可以直接从 dict 对象中获取值。
【讨论】：
json.dumps() 将字典转换为 str 对象，而不是 json(dict) 对象！所以你必须将你的str 加载到dict 中才能通过json.loads() 方法使用它
将json.dumps() 视为保存方法，将json.loads() 视为检索方法。
这是可以帮助您进一步理解它的代码示例：
import json
r = {'is_claimed': 'True', 'rating': 3.5}
r = json.dumps(r)
loaded_r = json.loads(r)
loaded_r['rating'] #Output 3.5
type(r) #Output str
type(loaded_r) #Output dict
【讨论】：
r 中拥有它，您不认为将json 加载回一个单独的变量loaded_r 有点低效吗？
将 r 定义为字典应该可以解决问题：
>>> r: dict = {'is_claimed': 'True', 'rating': 3.5}
>>> print(r['rating'])
3.5
>>> type(r)
<class 'dict'>
【讨论】：
json.dumps()用于解码JSON数据json.loads 将字符串作为输入并返回字典作为输出。json.dumps 将字典作为输入并返回一个字符串作为输出。import json
# initialize different data
str_data = 'normal string'
int_data = 1
float_data = 1.50
list_data = [str_data, int_data, float_data]
nested_list = [int_data, float_data, list_data]
dictionary = {
'int': int_data,
'str': str_data,
'float': float_data,
'list': list_data,
'nested list': nested_list
}
# convert them to JSON data and then print it
print('String :', json.dumps(str_data))
print('Integer :', json.dumps(int_data))
print('Float :', json.dumps(float_data))
print('List :', json.dumps(list_data))
print('Nested List :', json.dumps(nested_list, indent=4))
print('Dictionary :', json.dumps(dictionary, indent=4)) # the json data will be indented
输出：
String : "normal string"
Integer : 1
Float : 1.5
List : ["normal string", 1, 1.5]
Nested List : [
1,
1.5,
[
"normal string",
1,
1.5
]
]
Dictionary : {
"int": 1,
"str": "normal string",
"float": 1.5,
"list": [
"normal string",
1,
1.5
],
"nested list": [
1,
1.5,
[
"normal string",
1,
1.5
]
]
}
| Python | JSON |
|:--------------------------------------:|:------:|
| dict | object |
| list, tuple | array |
| str | string |
| int, float, int- & float-derived Enums | number |
| True | true |
| False | false |
| None | null |
nested_dictionary = {
'one': nested_list,
'two': dictionary,
}
json_dict = {'Nested Dictionary': nested_dictionary,
'Multiple':[nested_dictionary, nested_dictionary, nested_dictionary]
}
with open("test_nested.json", "w") as outfile:
json.dump(json_dict, outfile, indent=4, sort_keys=False)
图表响应
输出到test_nested.json
{
"Nested Dictionary": {
"one": [
1,
1.5,
[
"normal string",
1,
1.5
]
],
"two": {
"int": 1,
"str": "normal string",
"float": 1.5,
"list": [
"normal string",
1,
1.5
],
"nested list": [
1,
1.5,
[
"normal string",
1,
1.5
]
]
}
},
"Multiple": [
{
"one": [
1,
1.5,
[
"normal string",
1,
1.5
]
],
"two": {
"int": 1,
"str": "normal string",
"float": 1.5,
"list": [
"normal string",
1,
1.5
],
"nested list": [
1,
1.5,
[
"normal string",
1,
1.5
]
]
}
},
{
"one": [
1,
1.5,
[
"normal string",
1,
1.5
]
],
"two": {
"int": 1,
"str": "normal string",
"float": 1.5,
"list": [
"normal string",
1,
1.5
],
"nested list": [
1,
1.5,
[
"normal string",
1,
1.5
]
]
}
},
{
"one": [
1,
1.5,
[
"normal string",
1,
1.5
]
],
"two": {
"int": 1,
"str": "normal string",
"float": 1.5,
"list": [
"normal string",
1,
1.5
],
"nested list": [
1,
1.5,
[
"normal string",
1,
1.5
]
]
}
}
]
}
class 实例转 JSONclass Foo(object):
def __init__(
self,
data_str,
data_int,
data_float,
data_list,
data_n_list,
data_dict,
data_n_dict):
self.str_data = data_str
self.int_data = data_int
self.float_data = data_float
self.list_data = data_list
self.nested_list = data_n_list
self.dictionary = data_dict
self.nested_dictionary = data_n_dict
foo = Foo(
str_data,
int_data,
float_data,
list_data,
nested_list,
dictionary,
nested_dictionary)
# Because the JSON object is a Python dictionary.
result = json.dumps(foo.__dict__, indent=4)
# See table above.
# or with built-in function that accesses .__dict__ for you, called vars()
# result = json.dumps(vars(foo), indent=4)
print(result) # same as before
class Bar:
def toJSON(self):
return json.dumps(self, default=lambda o: o.__dict__,
sort_keys=False, indent=4)
bar = Bar()
bar.web = "Stackoverflow"
bar.type = "Knowledge"
bar.is_the_best = True
bar.user = Bar()
bar.user.name = "Milovan"
bar.user.age = 34
print(bar.toJSON())
图表响应
输出：
{
"web": "Stackoverflow",
"type": "Knowledge",
"is_the_best": true,
"user": {
"name": "Milovan",
"age": 34
}
}
【讨论】：
您可以在上面的示例中通过在默认字典中声明一个新字典来创建一个嵌套字典。
import json
dictionary = {
'fruit':{"Grapes": "10","color": "green"},
'vegetable':{"chilli": "4","color": "red"},
}
result = json.dumps(dictionary, indent = 3)
打印（结果）
这里，我使用了 indent=3
【讨论】：