it's all in the documentation:

repo = Repo.clone_from(cloneUrl, localRepopath)
remote = repo.create_remote(remote_name, url=another_url)
remote.push(refspec='{}:{}'.format(local_branch, remote_branch))

see also the push reference API. You can avoid the refspec setting if you set a tracking branch for the remote you want to push to.

I'm using gitpython==2.1.11 with Python 3.7. Below is my push function in which I first try a high-level push, and then a low-level push as necessary. Note how I check the return value of either command. I also log the push actions, and this explains what's happening at every step.

class GitCommandError(Exception):
    pass

class Git:
    def _commit_and_push_repo(self) -> None:
        repo = self._repo
        remote = repo.remote()
        remote_name = remote.name
        branch_name = repo.active_branch.name

        # Note: repo.index.entries was observed to also include unpushed files in addition to uncommitted files.
        log.debug('Committing repository index in active branch "%s".', branch_name)
        self._repo.index.commit('')
        log.info('Committed repository index in active branch "%s".', branch_name)

        def _is_pushed(push_info: git.remote.PushInfo) -> bool:
            valid_flags = {push_info.FAST_FORWARD, push_info.NEW_HEAD}  # UP_TO_DATE flag is intentionally skipped.
            return push_info.flags in valid_flags  # This check can require the use of & instead.

        push_desc = f'active branch "{branch_name}" to repository remote "{remote_name}"'
        log.debug('Pushing %s.', push_desc)
        try:
            push_info = remote.push()[0]
        except git.exc.GitCommandError:  # Could be due to no upstream branch.
            log.warning('Failed to push %s. This could be due to no matching upstream branch.', push_desc)
            log.info('Reattempting to push %s using a lower-level command which also sets upstream branch.', push_desc)
            push_output = repo.git.push('--set-upstream', remote_name, branch_name)
            log.info('Push output was: %s', push_output)
            expected_msg = f"Branch '{branch_name}' set up to track remote branch '{branch_name}' from '{remote_name}'."
            if push_output != expected_msg:
                raise RepoPushError(f'Failed to push {push_desc}.')
        else:
            is_pushed = _is_pushed(push_info)
            logger = log.debug if is_pushed else log.warning
            logger('Push flags were %s and message was "%s".', push_info.flags, push_info.summary.strip())
            if not is_pushed:
                log.warning('Failed first attempt at pushing %s. A pull will be performed.', push_desc)
                self._pull_repo()
                log.info('Reattempting to push %s.', push_desc)
                push_info = remote.push()[0]
                is_pushed = _is_pushed(push_info)
                logger = log.debug if is_pushed else log.error
                logger('Push flags were %s and message was "%s".', push_info.flags, push_info.summary.strip())
                if not is_pushed:
                    raise RepoPushError(f'Failed to push {push_desc} despite a pull.')
        log.info('Pushed %s.', push_desc)

Following is the code to git add, git commit and then git push using GitPython.

Install GitPython using pip install gitpython.

from git import Repo

PATH_OF_GIT_REPO = r'path\to\your\project\folder\.git'  # make sure .git folder is properly configured
COMMIT_MESSAGE = 'comment from python script'

def git_push():
    try:
        repo = Repo(PATH_OF_GIT_REPO)
        repo.git.add(update=True)
        repo.index.commit(COMMIT_MESSAGE)
        origin = repo.remote(name='origin')
        origin.push()
    except:
        print('Some error occured while pushing the code')    

git_push()

I've done something like creating a txt in a remote branch from newly created branch and commit, push to remote. Here's my code

import git
import datetime
import os
from time import *
from os import path
from git import Repo

def commit_files():
    if repo != None:
        new_branch = 'your_new_branch'
        current = repo.create_head(new_branch)
        current.checkout()
        master = self.repo.heads.master
        repo.git.pull('origin', master)
        #creating file
        dtime = strftime('%d-%m-%Y %H:%M:%S', localtime())
        with open(self.local_repo_path + path.sep + 'lastCommit' + '.txt', 'w') as f:
            f.write(str(dtime))
        if not path.exists(self.local_repo_path):
            os.makedirs(self.local_repo_path)
        print('file created---------------------')

        if repo.index.diff(None) or repo.untracked_files:

            repo.git.add(A=True)
            repo.git.commit(m='msg')
            repo.git.push('--set-upstream', 'origin', current)
            print('git push')
        else:
            print('no changes')

Solved it. First created a remote of the other repo

git remote add remote_to_push git@bitbucket...

Then the gitpython code

from git import Repo

repo = Repo('path/to/other/git/repo') #create repo object of the other repository
repo.git.checkout('remote_to_push/master') #checkout to a branch linked to the other repo
file = 'path/to/file' #path to file to push
repo.git.add(file) # same as git add file
repo.git.commit(m = "commit message") # same as git commit -m "commit message"
repo.git.push('remote_to_push', 'HEAD:master') # git push remote_to_push HEAD:master

Aside from the docs, I found the following to be quite helpful if anyone's struggling with gitpython as I found it quite a pain

Python Git Module experiences?

http://sandlininc.com/?p=801

Git push via GitPython

How to push to remote repo with GitPython