前言：

Vue框架：从项目学Vue
OJ算法系列：神机百炼 - 算法详解
Linux操作系统：风后奇门 - linux
C++11：通天箓 - C++11

应用场景：

读取一个json文件，利用其中某些键值对来构建一个新的json文件

• 如获取下列json文件中某几行的键值对，再构建一个json文件

{
	"packs": [{
		"_id": "1",
		"time": 123,
		"category": 0,
		"current_info": {
			"tag": ["timestamp"],
			"fps": 60.0,
			"time_stamp": 414.514,
			"name": "test"
		},
		"content": {
			"core": "service",
			"status": 0,
			"extraction": "client"
		}
	}]
}

基本工具：

文件操作：

打开文件：

• open(‘文件路径’, ‘打开方式’)：
  1. w：覆盖写
  2. r：只读
  3. wb：二进制写
  4. rb：二进制读

写文件：

• write(字符串)：
  字符串中转义字符：
  1. \r：切换到当前行的行首列
  2. \n：切换到下一行的同一列

file = open('Json文件地址', 'w')
lines = ''
for line in file:
	#line自动省略\r\n
    lines += line

读文件：

• open()返回一个可迭代对象：

file = open('Json文件地址', 'r')
lines = ''
for line in file:
	#line自动省略\r\n
    lines += line

关闭文件并刷新缓冲区：

• close：

file.close()

• close()后会自动刷新缓冲区，但有时你需要在关闭前刷新它，这时就可以使用 flush() 方法：

file.flush()

Json字符串和字典转换：

json.loads()：

• 用于将 字符串 加载为 字典

file = open('Json文件地址', 'r')
lines = ''
for line in file:
    lines += line
dic = json.loads(lines)
print(dic)

json.dumps():

• 用于将 字典 写入到 字符串

dic = {'packs': [{'_id': '1', 'time': 123, 'category': 0, 'current_info': {'tag': ['timestamp'], 'fps': 60.0, 'time_stamp': 414.514, 'name': 'test'}, 'content': {'core': 'service', 'status': 0, 'extraction': 'client'}}]}

json_str = json.dumps(dic)

print(json_str)

Json文件和字典转化：

json.load()：

• 用于将文件 加载为 字典

dictionary = json.load(open('原本的Json文件地址', 'r'))
print(dictionary)

json.dump():

• 用于将字典 写入到 文件，创建文件使用w模式打开

json.dump(ret, open("新的Json文件地址","w"))

集成上述API为函数：

def func(dictionary,*direct_key, **indirect_key):
    ret = {}
    for i in direct_key:
        ret[i] = dictionary[i]
    for i in indirect_key:
        ret[i] = {}
        print(type(ret), type(ret[i]), i)
        for j in indirect_key[i]:
            print(j)
            ret[i][j] = dictionary[i][j]
    return ret

ret = func(json.load('原来的Json文件地址'), '_id', 'end_time', 'frames', ext=['core_cm', 'extraction_cm'], statistics=['parsing_begin', 'parsing_end'])

json.dump(ret, open("新的Json文件地址","w"))

自己开发一个json.dump：

• 简化版，只能接收json最多二重字典，且最终value为str, int, 或float

import os
import json
def isIntOrFloatSeriously(number):
    result = False
    try:
        n = float(number)
        if str(number).count('.') != 0 or (n.is_integer() and str(number).count('.') == 0):
            result = True
    except:
        result = False
    return result

def func(dictionary,*direct_key, **indirect_key):
    amount = len(direct_key) + len(indirect_key)
    count = 1
    ret = ''
    for i in direct_key:
        ret += f"\"{i}\": "
        if isIntOrFloatSeriously(dictionary[i]) == True :
            ret += str(dictionary[i])
        else:
            ret += "\""+dictionary[i]+"\""
        if count < amount:
            ret += ","
        ret += "\r\n"
        count = count + 1
    for i in indirect_key:
        ret += f"\"{i}\": "+'{\r\n'
        inner_count = 1
        inner_amount = len(indirect_key[i])
        print(inner_amount, indirect_key[i])
        for j in indirect_key[i]:
            ret += f"\"{j}\": "
            if isIntOrFloatSeriously(dictionary[i][j]) == True :
                ret += str(dictionary[i][j])
            else:
                ret += "\""+dictionary[i][j]+"\""
            if inner_count < inner_amount:
                ret += ","
            ret += "\r\n"
            inner_count = inner_count + 1
        ret += "}"
        if count < amount:
            ret += ","
        ret += "\r\n"
        count = count + 1
    return ret

file = open('原本的Json文件地址')
lines = ''
for line in file:
    lines += line
dic = json.loads(lines)

ret = func(dic["packs"][0], '_id', 'end_time', 'frames', ext=['core_cm', 'extraction_cm'], statistics=['parsing_begin', 'parsing_end'])

file = open('新建的Json文件地址', 'w')
file.write('{\r\n')
file.write(ret)
file.write('}\r\n')
file.close()

扩展：

• Yaml文件格式
• Yaml文件 转化为 字典
  1. yaml.safe_load()：不省略float的.0
  2. yaml.load()：省略float的.0