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

Python3：

在使用urllib对参数进行URL编码后，调用

formdata = {
    "page_limit": "20",
    "page_start": "40"
}
data = parse.urlencode(formdata)

request.Request(url, data=data, headers=headers)

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

意思是，POST发送的数据必须是字节类型，不能为str类型。

解决方法：

  修改url编码为data = parse.urlencode(formdata).encode("UTF8")即可