Build multipart/form-data with files.

multipart.py

#vim: fileencoding=utf-8

import mimetools
import itertools

class MultiPartForm(object):

    def __init__(self):
        self.form_fields = []
        self.files = []
        self.boundary = mimetools.choose_boundary()

    def get_content_type(self):
        return 'multipart/form-data; boundary=%s' % self.boundary

    def add_field(self, name, value):
        self.form_fields.append((name, value))

    def add_file(self, fieldname, filename, body, mimetype):
        self.files.append((fieldname, filename, mimetype, body))

    def __str__(self):
        parts = []
        part_boundary = '--' + self.boundary

        parts.extend([
            part_boundary,
            'Content-Disposition: form-data; name="%s"' % name,
            '',
            value,
        ] for name, value in self.form_fields)

        parts.extend([
            part_boundary,
            'Content-Disposition: form-data; name="%s"; filename="%s"'\
                    % (field_name, filename),
            'Content-Type: %s' % content_type,
            '',
            body,
        ] for field_name, filename, content_type, body in self.files)

        flattened = list(itertools.chain(*parts))
        flattened.append('--' + self.boundary + '--')
        flattened.append('')
        return '\r\n'.join(flattened)