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Basic usage of JSON Library of Python standard library module

編輯：Python

Catalog

Preface

effect

loads,load Usage of

dumps,dump Usage of

Conclusion

Preface

json, Its full name is JavaScript Object Notation, That is to say JavaScript Object tag , Data is represented by a combination of objects and arrays , Although the structure is simple, the degree of structure is very high , Is a lightweight data exchange format .

effect

Mainly used to python Object code is json Format output or storage , And will be json Format object decoded as python object .

One JSON Objects can be written in the following form ：

[{ "name": " Xiao Ming ", "height": "170", "age": "18"}, { "name": " Xiaohong ", "height": "165", "age": "20"}]

Surrounded by brackets is equivalent to list type , Each element in the list can be of any type , In this case it's a dictionary type , Surrounded by braces .

JSON It can be freely combined from the above two forms , You can nest... Infinitely , The structure is clear , It's a great way to exchange data .

Let's take a look at json in loads, and load

loads,load Usage of

for example , There is a passage JSON String of form , It is str type , We use it json.loads convert to python Data structure of , Become a list or dictionary , So we can operate .

import jsondata = '''[{ "name": " Xiao Ming ", "height": "170", "age": "18"}, { "name": " Xiaohong ", "height": "165", "age": "20"}]'''# Print data type print(type(data))# json Type of data is converted to python Data of type new_data = json.loads(data)# Print data type print(type(new_data))

The operation results are as follows

In this way, we can use the index to get the corresponding content , For example, you want to get... In the first element name attribute , You can use the following methods ：

import jsondata = '''[{ "name": " Xiao Ming ", "height": "170", "age": "18"}, { "name": " Xiaohong ", "height": "165", "age": "20"}]'''# Print data type print(type(data))# json Type of data is converted to python Data of type new_data = json.loads(data)# Get content name = new_data[0]['name']new_name = new_data[0].get('name')# Print after conversion data type print(type(new_data))print(name)print(new_name)

Running results

That's all loads Usage of .

load The usage of is to put json Format file , convert to python Data of type .

Be careful ：load Method operates on the entire file object , Here is to convert the contents of the whole file object into json object .（ The following figure shows the operation object ）

Example

import jsonimport json# load The usage of is to put json Format file , convert to python Data of type .# The file object that builds the file with open('test1.json',encoding='utf-8')as fp: # Load the long file object , Convert to python Data of type pyth_list = json.load(fp) print(pyth_list) print(type(pyth_list)) print(type(pyth_list[0]))

A file operation object running result is required

That's all loads and load Usage of , Both methods can be used in appropriate scenarios .

dumps,dump Usage of

json.dumps() function , hold python Type of data to json character string

json.dump() function , hold python Type of data to json Save format to file

dumps function

import jsondata = '''[{ "name": " Xiao Ming ", "height": "170", "age": "18"}, { "name": " Xiaohong ", "height": "165", "age": "20"}]'''# Print coming data type print(type(data))# json Type of data is converted to python Data of type new_data = json.loads(data)# hold python Type of data to json character string lit = json.dumps(new_data)# Print after conversion data type print(type(new_data))print(type(lit))

Running results

Actually loads and dumps The usage of is consistent ,loads Yes, it will json Type of data is converted to python Data of type , and dumps Yes, it will json Type of data is converted to python Data of type . One is encoding and the other is decoding .

dump function

hold python Type of data to json Save format to file

import jsonimport jsondata = '''[{ "name": " Xiao Ming ", "height": "170", "age": "18"}, { "name": " Xiaohong ", "height": "165", "age": "20"}]'''# json Type of data is converted to python Data of type new_data = json.loads(data)# hold python Type of data to json Save format to file # Build the object to write to the file with open('test1.json','w',encoding='utf-8')as fp: # hold python Type of data to json Save format to file json.dump(new_data,fp,ensure_ascii=False)

In order to output Chinese , You also need to specify parameters ensure_ascii by False

Save files

Conclusion

This is about python Standard library module json This is the end of the article on the basic usage of the library , More about python Standard library module json Please search the previous articles of SDN or continue to browse the related articles below. I hope you will support SDN more in the future ！