python 如何将字典写为json文件

res = {
    "data":[]
}
temp = {
        "name":name,
        "cls":cls
}
res["data"].append(temp)

json_data = json.dumps(res)
with open('E:/res.json', 'a') as f_six:
    f_six.write(json_data)

import json
dic = {  
    'andy':{  
        'age': 23,  
        'city': 'beijing',  
        'skill': 'python'  
    },  
    'william': {  
        'age': 25,  
        'city': 'shanghai',  
        'skill': 'js'  
    }  
}  
js = json.dumps(dic)   
file = open('test.txt', 'w')  
file.write(js)  
file.close()  

import json
file = open('test.txt', 'r') 
js = file.read()
dic = json.loads(js)   
print(dic) 
file.close() 

dic = {  
    'andy':{  
        'age': 23,  
        'city': 'beijing',  
        'skill': 'python'  
    },  
    'william': {  
        'age': 25,  
        'city': 'shanghai',  
        'skill': 'js'  
    }  
} 
fw = open("test.txt",'w+')
fw.write(str(dic))      #把字典转化为str
fw.close()

fr = open("test.txt",'r+')
dic = eval(fr.read())   #读取的str转换为字典
print(dic)
fr.close()