Integrating WeChat Pay with a Flask Backend and Mini Program

Development Environment

Local: Windows 10, Python 2.7.13 (64‑bit), Flask 0.12.2.

Online: CentOS 6.5, Python 2.7.13 (64‑bit), Flask 0.12.2.

1. Write the backend program

Review the unified order API. Two important points: a) the user identifier (openid) is required when trade_type=JSAPI; b) the request must be signed.

Generate the signature.

Set the parameters to be signed (include openid, otherwise the signature will be incorrect).

Example data dictionary:

data = {<br>    'appid': appid,<br>    'mch_id': mch_id,<br>    'nonce_str': get_nonce_str(),<br>    'body': '测试',  # product description<br>    'out_trade_no': str(int(time.time())),  # merchant order number<br>    'total_fee': '1',<br>    'spbill_create_ip': spbill_create_ip,<br>    'notify_url': notify_url,<br>    'attach': '{"msg": "自定义数据"}',<br>    'trade_type': trade_type,<br>    'openid': '1111111111111111111111'<br>}

Sort the parameters, concatenate the merchant key, and compute the MD5 hash:

stringA = '&'.join(["{0}={1}".format(k, pay_data.get(k)) for k in sorted(pay_data)])<br>stringSignTemp = '{0}&key={1}'.format(stringA, self.merchant_key)<br>sign = hashlib.md5(stringSignTemp).hexdigest()

Add the generated MD5 as the sign field, convert the dictionary to XML, and POST it to the WeChat API to obtain prepay_id :

data['sign'] = md5<br>req = urllib2.Request(url, data, headers={'Content-Type': 'application/xml'})<br>result = urllib2.urlopen(req, timeout=timeout).read()

Generate the parameters required by wx.requestPayment in the mini‑program, noting that the package field must be prepay_id=YOUR_PREPAY_ID :

paySign_data = {<br>    'appId': appId,<br>    'timeStamp': timeStamp,<br>    'nonceStr': nonceStr,<br>    'package': 'prepay_id={0}'.format(prepay_id),<br>    'signType': 'MD5'<br>}

Follow the same signing steps (including the merchant key) to create paySign . Return all these fields to the mini‑program.

2. Write the mini‑program

Create a quick project.

Call the backend endpoint to get the payment parameters and invoke wx.requestPayment directly.

wx.request({<br>    url: 'http://127.0.0.1:5000/wxpay/pay',<br>    header: {'content-type': 'application/json'},<br>    success: function (res) {<br>        wx.requestPayment({<br>            timeStamp: res.data.timeStamp,<br>            nonceStr: res.data.nonceStr,<br>            package: res.data.package,<br>            signType: res.data.signType,<br>            paySign: res.data.paySign,<br>            success: function (res) { console.log(res) },<br>            fail: function (res) { console.log(res) }<br>        })<br>    }<br>})

WeChat will send a POST notification (XML) to the server after payment. The server should verify the data and respond with XML indicating success:

'return_code': 'SUCCESS',<br>'return_msg': 'OK'

Disclaimer: This article is compiled from online sources; copyright belongs to the original author. If any rights are infringed, please contact us for removal or authorization.