json是一种轻量级数据交换格式，常用于http请求中，在日常运维工作中经常可以看到
1.json类型和python数据的转换
函数转换对应关系表：
| Python | JSON |
| dict | object |
| list, tuple | array |
| str, unicode | string |
| int, long, float | number |
| True | true |
| False | false |
| None | null |
1）将json数据写入文件：json.dump()
例子：
import json
json_data = {"a":1,"b":2,"c":3,"d":4,"e":5,"f":6}
f = open("a.txt","w")
json.dump(json_data,f)
f.close()
结果：目录下生成a.txt文件，内容：
{"a": 1, "c": 3, "b": 2, "e": 5, "d": 4, "f": 6}
2)读取文件中json数据，显示为unicode类型格式：json.load()
import json
# json_data = {"a":1,"b":2,"c":3,"d":4,"e":5,"f":6}
# f = open("a.txt","w")
# json.dump(json_data,f)
# f.close()
f2 = open("a.txt","r")
dict2 = json.load(f2)
print(dict2)
结果：
{u'a': 1, u'c': 3, u'b': 2, u'e': 5, u'd': 4, u'f': 6}
3）python字典—>（转换）json字符串：json.dumps()
例子：
import json
m = {"success":"yes","message":"hello"}
json_str = json.dumps(m)
print(m)
print(type(m))
print(json_str)
print(type(json_str))
结果：
{'message': 'hello', 'success': 'yes'}
<type 'dict'>
{"message": "hello", "success": "yes"}
<type 'str'>
4）json字符串—>（解码）pyhton字典:json.loads()
例子：
import json
m = {"success":"yes","message":"hello"}
json_str = json.dumps(m)
print(json_str)
print(type(json_str))
json_dict = json.loads(json_str)
print(json_dict)
print(type(json_dict))
结果：
{"message": "hello", "success": "yes"}
<type 'str'>
{u'message': u'hello', u'success': u'yes'}
<type 'dict'>
2.爬虫举例
import json
import urllib2
from pip._vendor.requests.packages import chardet
url = 'http://'
req = urllib2.Request(url)
res = urllib2.urlopen(req)
result = res.read()
print(chardet.detect(result))
m = json.loads(result)
print(type(m))
print(m)
