Python中的 json.dumps()

JSON 的完整形式是 JavaScript Object Notation。这意味着由编程语言中的文本组成的脚本（可执行）文件用于存储和传输数据。 Python通过一个名为 json 的内置包支持 JSON。要使用此功能，我们在Python脚本中导入 json 包。 JSON中的文本是通过quoted-string完成的，该字符串包含{}内键值映射中的值。它类似于Python中的字典。
注意：有关详细信息，请参阅使用Python读取、写入和解析 JSON

json.dumps()

json.dumps()函数将Python对象转换为 json字符串。

Syntax: 
json.dumps(obj, *, skipkeys=False, ensure_ascii=True, check_circular=True, allow_nan=True, cls=None, indent=None, separators=None, default=None, sort_keys=False, **kw)
Parameters: 
obj:Serialize obj as a JSON formatted stream 
skipkeys:If skipkeys is true (default: False), then dict keys that are not of a basic type (str, int, float, bool, None) will be skipped instead of raising a TypeError. 
ensure_ascii:If ensure_ascii is true (the default), the output is guaranteed to have all incoming non-ASCII characters escaped. If ensure_ascii is false, these characters will be output as-is. 
check_circular :If check_circular is false (default: True), then the circular reference check for container types will be skipped and a circular reference will result in an OverflowError (or worse). 
allow_nan :If allow_nan is false (default: True), then it will be a ValueError to serialize out of range float values (nan, inf, -inf) in strict compliance of the JSON specification. If allow_nan is true, their JavaScript equivalents (NaN, Infinity, -Infinity) will be used. 
indent:If indent is a non-negative integer or string, then JSON array elements and object members will be pretty-printed with that indent level. An indent level of 0, negative, or “” will only insert newlines. None (the default) selects the most compact representation. Using a positive integer indent indents that many spaces per level. If indent is a string (such as “\t”), that string is used to indent each level. 
separators :If specified, separators should be an (item_separator, key_separator) tuple. The default is (‘, ‘, ‘: ‘) if indent is None and (‘, ‘, ‘: ‘) otherwise. To get the most compact JSON representation, you should specify (‘, ‘, ‘:’) to eliminate whitespace. 
default:If specified, default should be a function that gets called for objects that can’t otherwise be serialized. It should return a JSON encodable version of the object or raise a TypeError. If not specified, TypeError is raised. 
sort_keys :If sort_keys is true (default: False), then the output of dictionaries will be sorted by key. 
 

示例 #1：将Python字典传递给 json.dumps()函数将返回一个字符串。

Python3

import json
 
# Creating a dictionary
Dictionary ={1:'Welcome', 2:'to',
            3:'Geeks', 4:'for',
            5:'Geeks'}
  
# Converts input dictionary into
# string and stores it in json_string
json_string = json.dumps(Dictionary)
print('Equivalent json string of input dictionary:',
      json_string)
print("        ")
 
# Checking type of object
# returned by json.dumps
print(type(json_string))

输出

Equivalent json string of dictionary: {“1”: “Welcome”, “2”: “to”, “3”: “Geeks”, “4”: “for”, “5”: “Geeks”} 

示例 #2：通过将 skipkeys 设置为 True（默认值：False），我们会自动跳过非基本类型的键。

Python3

import json
 
 
Dictionary ={(1, 2, 3):'Welcome', 2:'to',
            3:'Geeks', 4:'for',
            5:'Geeks'}
 
 
# Our dictionary contains tuple
# as key, so it is automatically
# skipped If we have not set
# skipkeys = True then the code
# throws the error
json_string = json.dumps(Dictionary,
                         skipkeys = True)
 
print('Equivalent json string of dictionary:',
      json_string)

输出

Equivalent json string of dictionary: {“2”: “to”, “3”: “Geeks”, “4”: “for”, “5”: “Geeks”} 
 

示例#3：

Python3

import json
 
 
# We are adding nan values
# (out of range float values)
# in dictionary
Dictionary ={(1, 2, 3):'Welcome', 2:'to',
            3:'Geeks', 4:'for',
            5:'Geeks', 6:float('nan')}
 
# If we hadn't set allow_nan to
# true we would have got
# ValueError: Out of range float
# values are not JSON compliant
json_string = json.dumps(Dictionary,
                         skipkeys = True,
                         allow_nan = True)
 
print('Equivalent json string of dictionary:',
      json_string)

输出 ：

Equivalent json string of dictionary: {“2”: “to”, “3”: “Geeks”, “4”: “for”, “5”: “Geeks”, “6”: NaN} 

示例 #4：

Python3

import json
 
 
Dictionary ={(1, 2, 3):'Welcome', 2:'to',
            3:'Geeks', 4:'for',
            5:'Geeks', 6:float('nan')}
 
# Indentation can be used
# for pretty-printing
json_string = json.dumps(Dictionary,
                         skipkeys = True,
                         allow_nan = True,
                         indent = 6)
 
print('Equivalent json string of dictionary:',
      json_string)

输出：

Equivalent json string of dictionary: {
      "2": "to",
      "3": "Geeks",
      "4": "for",
      "5": "Geeks",
      "6": NaN
}

示例 #5：

Python3

import json
 
Dictionary ={(1, 2, 3):'Welcome', 2:'to',
            3:'Geeks', 4:'for',
            5:'Geeks', 6:float('nan')}
 
# If specified, separators should be
# an (item_separator, key_separator)tuple
# Items are separated by '.' and key,
# values are separated by '='
json_string = json.dumps(Dictionary,
                         skipkeys = True,
                         allow_nan = True,
                         indent = 6,
                         separators =(". ", " = "))
 
print('Equivalent json string of dictionary:',
      json_string)

输出：

Equivalent json string of dictionary: {
      "2" = "to". 
      "3" = "Geeks". 
      "4" = "for". 
      "5" = "Geeks". 
      "6" = NaN
}

示例 #6：

Python3

import json
 
Dictionary ={'c':'Welcome', 'b':'to',
            'a':'Geeks'}
 
json_string = json.dumps(Dictionary,
                         indent = 6,
                         separators =(". ", " = "),
                         sort_keys = True)
 
print('Equivalent json string of dictionary:',
      json_string)

输出：

Equivalent json string of dictionary: {
      "a" = "Geeks". 
      "b" = "to". 
      "c" = "Welcome"
}