Pandas Dataframe update cell value in SessionState

[chris_klose]

Hey guys,

quick question. Is there a way preserve a pandas dataframe while using SessionState?
I copyed the file (“sessionState.py”) into my project and load it.

However, if I do an update for one row of the dataframe, the previous values get lost.

state = SessionState.get(df=pd.DataFrame(), index =0)

if st.button("Next"):
state.df.at[state.index, 'Added Values'] = 1
state.index += 1

st.dataframe(state.df)

Any ideas why this is and how to solve it?

Thanks in advance.
Chris

[ash2shukla]

Its because your state’s df and index variables are getting reset everytime your script executes,

you could do something like this,
( Assuming you are using Session State class from this gist https://gist.github.com/Ghasel/0aba4869ba6fdc8d49132e6974e2e662 )

state = SessionState()

if state.df is None:
    state.df = pd.DataFrame()

if state.index is None:
    state.index = 0

[chris_klose]

Sounds pritty easy. The wired thing is, the state.index is not reseted. Only the df.
I took the file from here: https://gist.github.com/tvst/036da038ab3e999a64497f42de966a92 .
If i try to do

pages[page](state)

than it says that 0 parameters were required but one given.
Also state.snyc() does not work. Something is odd here.

Further, when I copy your code from the gist and do
state = _SessionState() I get:
TypeError: init() missing 2 required positional arguments: ‘session’ and ‘hash_funcs’

Any ideas how to solve that?

[ash2shukla]

Hey @chris_klose

Please use the get_state function to get the state.
I like to use a small decorator that I wrote that takes care of get_state and sync state.
Check this out,

ash2shukla/streamlit-heroku/blob/master/src/utils.py

ash2shukla/streamlit-heroku/blob/master/main.py

Also I like to put the “default configs” in the utils file like this, but it depends how you want to do it, https://github.com/ash2shukla/streamlit-heroku/blob/be0fd199cd772c7241f0aac1f59c626923c0df11/src/utils.py#L93

Hope it helps !