flask使用wechatpy回覆消息

from flask import Flask
from flask import request
import hashlib
from wechatpy import parse_message, create_reply
from wechatpy.utils import check_signature
from wechatpy.exceptions import InvalidSignatureException
from wechatpy.replies import TextReply

app = Flask(__name__)

@app.route('/', methods=['GET', 'POST'])
def index():
	if request.method == 'GET':
		signature = request.args.get('signature')		
		timestamp = request.args.get('timestamp')
		nonce = request.args.get('nonce')
		token = 'zzmtkj'

		echostr = request.args.get('echostr')

		try:
		    echostr = check_signature(token, signature, timestamp, nonce)
		except InvalidSignatureException:
			print('error')

		
		if signature == sha1_signature:
			return echostr	
	elif request.method == 'POST':
		msg = parse_message(request.get_data())
		if msg.type == 'text':
			reply = create_reply('這是條文字消息', msg)
		if msg.type == 'image':
			reply = create_reply('這是條圖片消息', msg)
	return reply.render()