click-login.py

import click

@click.command()
def login():
    password = click.prompt('Password: ', hide_input=True)
    session_token = ''.join(reversed(password))  # exchange password for session token in some way
    click.echo('export MY_SESSION_TOKEN="{}"'.format(session_token))

if __name__ == '__main__':
    login()

# Called from bash with: eval $(python click-login.py)