Table of contents
1. Basic overview of JSON
JSON is language independent
JSON is self-describing and easier to understand
JSON is smaller, faster and easier to parse than XML
2. JSON format
{
"student":
[
{"name": "小明", "age": 12},
{"name": "小红", "age": 18}
],
"classroom": {"class1": "room1", "class2": "room2"}
}3. Precautions
1. The key part of the key-value pair of json must use double quotes
2. The value part of the key-value pair of json does not allow function, undefined, NaN, but can have null
3. After the json data ends, meaningless commas are not allowed
4. Summary of json format
{"name": "admin", "age": 18} # JSON对象
# JSON数组
{
"student":
[
{"name": "小明", "age": 12},
{"name": "小红", "age": 18}
],
}
5. JSON module
5.1 Function
1. Use json string to generate python object (load)
2. Use python object formatting called json string (dump)
5.2 Data type conversion
Convert python to json format, there will be changes in data types
dict--object
list,tuple--array
str--string
int,float--number
True--true
False--false
None--null
2.3 How to use
json.dumps(obj) # convert the python data type to a string in json format
json.dump(obj,fp) # Convert and save the python data type string to a file in json format
json.loads(s) # Convert a string in json format to a python type
json.load(fp) # read the data from the file in json format and convert it to python type
2.4 json.dumps（）
The difference between the json format and the python format is that the print output in the python format is a single quote, and the type is dict, and the print output in the json format is double quotes, and the type is str. There is a difference in capitalization at the beginning of True.
import json
person = {"name": "小明", "age": 18, "tel": ["888888", "13555555555"], "isonly": True}
print(person)
print(type(person))
print(json.dumps(person))
print(type(json.dumps(person)))Use parameters to format the output of the json string
Interpretation of parameters:
sort_keys # whether to sort
indent # Define the indentation distance
separators # is a tuple that defines the separator type
skipkeys # Whether to allow json strings to encode dictionary objects, the key of the dictionary is not a string type (not allowed by default)
print(json.dumps(person, sort_keys=True, indent=4, separators=(',', ':')))import json
person = {"name": "小明", "age": 18, "tel": ["888888", "13555555555"], "isonly": True}
print(person)
print(type(person))
print(json.dumps(person, sort_keys=True, indent=4, separators=(',', ':')))
print(type(json.dumps(person)))
json_str = json.dumps(person)
with open('test.json', 'w', encoding='utf-8') as f:
f.write(json_str)2.5 json.dump()
Convert python data type and save to json format file
person = {"name": "小明", "age": 18, "tel": ["888888", "13555555555"], "isonly": True}
json.dump(person, open('data.json', 'w'), sort_keys=True, indent=4, separators=(',', ':'))The difference between json.dumps() and json.dump writing files
dump() does not need to use the .write() method, just which dictionary and which file to write, and dumps() needs to be written using the .writer() method
If you write the dictionary into a file, dump() is easy to use, but if you don’t need to operate the file, or store the content in a database or excel, you need to use dumps() to convert the field to a string first, and then write enter.
2.6 json.loads()
Convert a string in json format to a python type
json_str = json.dumps(person, sort_keys=True, indent=4, separators=(',', ':'))
python_dict = json.loads(json_str)
print(python_dict)
print(type(python_dict))
print(python_dict.keys())
print(python_dict.values())
file operation
f = open('data.json', 'r', encoding='utf-8')
content = f.read()
python_dict = json.loads(content)
print(python_dict)2.7 json.load()
Read data from a file in json format and convert it to a python type
python_dict = json.load(open('data.json', 'r'))
print(python_dict)
print(type(python_dict))The difference between json.loads and json.load:
loads() wears a json string, while load() passes a file object
When using loads(), you need to read the file before using it, but load() does not
3. Parse the json file
python_dict = json.load(open('data.json', 'r'))
print(python_dict)
print(type(python_dict))
print(python_dict.keys())
print(python_dict.values())
print(python_dict['age'])