TypeError: POST data should be bytes, an iterable of bytes, or a file object. It cannot be of type s

TypeError: POST data should be bytes, an iterable of bytes, or a file
object. It cannot be of type str.

这是因为POST数据需要是字节或文件句柄对象，不能是字符，转换一下（encode）就好了：

data = urllib.parse.urlencode(formData).encode("utf-8")
request = urllib.request.Request(url, data=data, headers=header)
print(urllib.request.urlopen(request).read().decode("utf-8"))