NameError: name 'service' is not defined Google API

I want to upload a photo to google drive. I can read the files that are on the drive. But when I ad the uploading part, I keep getting the same error. I keep getting the error "NameError: name 'service' is not defined" I have every library imported but still doesn't work This is my code I've looked around but haven't seen a post explaining it.

from __future__ import print_function
import pickle
import os.path
from googleapiclient.discovery import build
from google_auth_oauthlib.flow import InstalledAppFlow
from google.auth.transport.requests import Request
from apiclient.http import MediaFileUpload


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

def main():
"""Shows basic usage of the Drive v3 API.
Prints the names and ids of the first 10 files the user has access to.
"""
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:
        creds = pickle.load(token)
# If there are no (valid) credentials available, let the user log in.
if not creds or not creds.valid:
    if creds and creds.expired and creds.refresh_token:
        creds.refresh(Request())
    else:
        flow = InstalledAppFlow.from_client_secrets_file(
            'client_secret.json', SCOPES)
        creds = flow.run_local_server(port=0)
    # Save the credentials for the next run
    with open('token.pickle', 'wb') as token:
        pickle.dump(creds, token)

service = build('drive', 'v3', credentials=creds)


# Call the Drive v3 API
results = service.files().list(
    pageSize=10, fields="nextPageToken, files(id, name)").execute()
items = results.get('files', [])

if not items:
    print('No files found.')
else:
    print('Files:')
    for item in items:
        print(u'{0} ({1})'.format(item['name'], item['id']))

if __name__ == '__main__':
main()

file_metadata = {'name': 'unnamed.jpg'}
media = MediaFileUpload('unnamed.jpg',
                    mimetype='image/jpeg')
file = service.files().create(body=file_metadata,
                                media_body=media,
                                fields='id').execute()
print ('File ID: %s' % file.get('id'))

Your code formatting is not clear, but I expect that your problem is service is defined inside your main function as service = build('drive', 'v3', credentials=creds). However, you then try to use it outside of the function in the if __name__ == "__main__" block. This will not work as the variable does not exist in this scope.

You either need to redefine service in this scope, before the line

file = service.files().create(body=file_metadata,
                                media_body=media,
                                fields='id').execute()

or you can return service from your main function and use service = main().