post_form_urllib.py

#!/usr/bin/env python3
import mimetypes
import uuid
import io
import os


class FormData(object):
    def __init__(self, data=None, files=None):
        self.boundary = uuid.uuid4().hex
        self._content = io.BytesIO()

        for name, value in (data or {}).items():
            self.write_part(value=value, name=name)

        for name, path in (files or {}).items():
            with open(path, 'rb') as fd:
                ct = mimetypes.guess_type(path)[0] or 'application/octet-stream'
                self.write_part(value=fd.read(), name=name,
                                filename=os.path.basename(path),
                                content_type=ct)

    def write_part(self, value, content_type=None, **kwargs):
        params = ''.join([f'; {k}="{v}"' for k, v in kwargs.items()])
        ct = f'\r\nContent-Type: {content_type}' if content_type else ''
        self._content.write(
            f'--{self.boundary}\r\n'
            f'Content-Disposition: form-data{params}{ct}\r\n\r\n'.encode())
        if isinstance(value, str):
            value = value.encode()
        self._content.write(value + b'\r\n')

    @property
    def content_type(self):
        return f'multipart/form-data; boundary={self.boundary}'

    @property
    def body(self):
        return self._content.getvalue() + \
               f'--{self.boundary}--\r\n'.encode()


data = FormData(data={'name': 'value'},
                files={'file': __file__})


from urllib.request import Request, urlopen
with urlopen(Request(url='https://httpbin.org/post',
                     data=data.body,
                     headers={'Content-Type': data.content_type})) as response:
    print(response.status)
    print(response.headers)
    print(response.read().decode())


import http.client
conn = http.client.HTTPSConnection(host='httpbin.org')
conn.request(method='POST', url='/post', body=data.body,
             headers={'Content-Type': data.content_type})
response = conn.getresponse()
print(response.status)
print(response.headers)
print(response.read().decode())