downloads all files in a google drive folder keeping the folder structure.

download_from_drive.py

from __future__ import print_function
import pickle
import io
import argparse
import sys
import os.path
from pathlib import Path
from googleapiclient.discovery import build
from google_auth_oauthlib.flow import InstalledAppFlow
from google.auth.transport.requests import Request
from apiclient.http import MediaIoBaseDownload

class GoogleDriveService:
    # If modifying these scopes, delete the file token.pickle.
    SCOPES = ['https://www.googleapis.com/auth/drive']

    def __init__(self):
        self.load_creds()
        self.client = build('drive', 'v3', credentials=self.creds)

    def load_creds(self):
        self.creds = None
        # The file token.pickle stores the user's access and refresh tokens, and is
        # created automatically when the authorization flow completes for the first
        # time.
        if os.path.exists('token.pickle'):
            with open('token.pickle', 'rb') as token:
                self.creds = pickle.load(token)
        # If there are no (valid) credentials available, let the user log in.
        if not self.creds or not self.creds.valid:
            if self.creds and self.creds.expired and self.creds.refresh_token:
                self.creds.refresh(Request())
            else:
                flow = InstalledAppFlow.from_client_secrets_file(
                    './../credentials.json', GoogleDriveService.SCOPES)
                if REMOTE_RUN:
                    self.creds = flow.run_console()
                else:
                    self.creds = flow.run_local_server(port=0)
            # Save the credentials for the next run
            with open('./../token.pickle', 'wb') as token:
                pickle.dump(self.creds, token)

    def download_file(self, file_id, file_name, file_path='./', verbose=False):
        request = self.client.files().get_media(fileId=file_id)
        fh = io.FileIO((file_path + file_name), 'wb')
        downloader = MediaIoBaseDownload(fh, request)
        done = False
        while done is False:
            status, done = downloader.next_chunk()
            if verbose:
                print("%s%s - Download %d%%." % (file_path, file_name, int(status.progress() * 100)))

    def download_all_files_in_folder(self, folder_id, file_path='./'):
        # creates path if does not exist
        if not os.path.exists(file_path):
            os.makedirs(file_path)
        page_token = None
        while(True):
            # Call the Drive v3 API
            results = self.client.files().list(
                q=("'%s' in parents" % folder_id),
                fields="nextPageToken, files(id, name, mimeType, parents)", pageToken=page_token
            ).execute()
            items = results.get('files', [])

            if not items:
                print('No files found in %s' % file_path)
            else:
                for item in items:
                    if item['mimeType'] == 'application/vnd.google-apps.folder':
                        # continue
                        new_path = ('%s%s/' % (file_path, item['name'].replace('/','\/')))
                        self.download_all_files_in_folder(item['id'], new_path)
                    else:
                        download_name = item['name'].replace('/','-')
                        # handle avatar files without extension
                        if (item['mimeType'] == 'image/jpeg') and not ('.jpeg' in download_name):
                            download_name += '.jpeg'
                        full_path_file_name = file_path + download_name
                        if os.path.exists(full_path_file_name):
                            print("%s - already exists." % (full_path_file_name))
                        else:
                            try:
                                self.download_file(item['id'], download_name, file_path, verbose=True)
                            except:
                                e = sys.exc_info()[0]
                                error_file = open('./../download_errors.txt', 'a+')
                                error_file.write("Couldn't download %s%s (%s) - Error: %s\n" % (file_path, download_name, item['id'], e))
                                error_file.close()

            page_token = results.get('nextPageToken', None)
            if page_token is None:
                break


def main():
    gdrive_service = GoogleDriveService()
    # uncomment line below for debugging
    # import code; code.interact(local=dict(globals(), **locals()))
    gdrive_service.download_all_files_in_folder(PARENT_FOLDER_ID)


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='Download files stored in Google Drive.')
    parser.add_argument('--folder_id', dest='folder_id', help='parent folder id. If none given, all files are downloaded')
    parser.add_argument('--remote', dest='remote', default=False, help='set to true if running remotely. Eg via SSH. default: false')

    args = parser.parse_args()
    PARENT_FOLDER_ID = args.folder_id
    REMOTE_RUN  = bool(args.remote)

    main()

before running it you should enable the Google Drive API, generate and save the credentials.json file and install dependencies.
You can find more information on steps 1 and 2 of this Quickstart document