app/SessionState.py

"""Hack to add per-session state to Streamlit.
Usage
-----
>>> import SessionState
>>>
>>> session_state = SessionState.get(user_name='', favorite_color='black')
>>> session_state.user_name
''
>>> session_state.user_name = 'Mary'
>>> session_state.favorite_color
'black'
Since you set user_name above, next time your script runs this will be the
result:
>>> session_state = get(user_name='', favorite_color='black')
>>> session_state.user_name
'Mary'
"""
from streamlit.scriptrunner import get_script_run_ctx
from streamlit.server.server import Server


class SessionState(object):
    def __init__(self, **kwargs):
        """A new SessionState object.
        Parameters
        ----------
        **kwargs : any
            Default values for the session state.
        Example
        -------
        >>> session_state = SessionState(user_name='', favorite_color='black')
        >>> session_state.user_name = 'Mary'
        ''
        >>> session_state.favorite_color
        'black'
        """
        for key, val in kwargs.items():
            setattr(self, key, val)


def get(**kwargs):
    """Gets a SessionState object for the current session.
    Creates a new object if necessary.
    Parameters
    ----------
    **kwargs : any
        Default values you want to add to the session state, if we're creating a
        new one.
    Example
    -------
    >>> session_state = get(user_name='', favorite_color='black')
    >>> session_state.user_name
    ''
    >>> session_state.user_name = 'Mary'
    >>> session_state.favorite_color
    'black'
    Since you set user_name above, next time your script runs this will be the
    result:
    >>> session_state = get(user_name='', favorite_color='black')
    >>> session_state.user_name
    'Mary'
    """
    # Hack to get the session object from Streamlit.

    ctx = get_script_run_ctx()

    this_session = None

    current_server = Server.get_current()
    if hasattr(current_server, '_session_infos'):
        # Streamlit < 0.56
        session_infos = Server.get_current()._session_infos.values()
    else:
        session_infos = Server.get_current()._session_info_by_id.values()

    for session_info in session_infos:
        s = session_info.session
        if (
            (not hasattr(s, '_main_dg') and s._uploaded_file_mgr == ctx.uploaded_file_mgr)
        ):
            this_session = s

    if this_session is None:
        raise RuntimeError(
            "Oh noes. Couldn't get your Streamlit Session object. "
            'Are you doing something fancy with threads?')

    # Got the session object! Now let's attach some state into it.

    if not hasattr(this_session, '_custom_session_state'):
        this_session._custom_session_state = SessionState(**kwargs)

    return this_session._custom_session_state

__all__ = ['get']