python修改json文件的value

#!/usr/bin/python
# coding=utf-8
import sys
import json
import argparse
reload(sys)
sys.setdefaultencoding('utf-8')

def PrepareParser():
    result=argparse.ArgumentParser(description="get data from jenkins")
    result.add_argument("-jf","--jsonfile",help="jsonfile", required=True)
    result.add_argument("-p","--platform",help="platform", required=True)
    result.add_argument("-v","--app_version",help="app_version", required=True)
    print result
    return result
parser=PrepareParser()
args=parser.parse_args()
json_file=args.jsonfile
platform=args.platform
app_version=args.app_version

with open(json_file, 'rb') as f:
    json_data = json.load(f)
    for item in json_data:
        if item["platform"]==platform:
            item["ver"] = app_version
        out = file(json_file, 'w+')
        reContent = json.dump(json_data, out, ensure_ascii=False, indent=4)