Calls read function after file upload

🎈 Using Streamlit
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1

Summary

Hi, I have an app which accepts file upload. When I upload, it calls a read function. Then from the file, I show some options as multiselect, when I submit the multiselect option, the read function calls again. I tried caching or session state but it is not working. Can someone help?

Steps to reproduce

Code snippet:

@st.cache_data(show_spinner=False)
def read_file(file):
    with tempfile.NamedTemporaryFile(mode="wb") as temp:
        with st.spinner('This may take a while. Wait for it...'):
            bytes_data = file.getvalue()
            temp.write(bytes_data)
            df = MyFunctionReadsFromPathAndAggregations(temp.name)
            return df


def app():
    session_state = st.session_state
    if "df" not in session_state:
        file = st.file_uploader("Upload file.")
        if file is not None:
            df = read_file(file)
            with st.form(key='my_form_to_submit'):
                selected_authors = st.multiselect(
                    "Choose authors of the group",
                    df.author.unique().tolist())
            
                submit_button = st.form_submit_button(label='Submit')

            if submit_button:
                  # do the things

Expected behavior:

I expect to run my function inside read_file once. After reading, I show some keys from dataframe as multiselect, then user selects the scope and submits. Now it should not read dataframe again.

Actual behavior:

After clicking submit, it recalls read_file again.

Debug info

2

The function is called after submitting because your code calls it, but the dataframe is not read again, the cached value is returned instead.

3

I’m not sure I followed. I’ve uploaded two log screenshots. As you can see, it seems like it does the operations once again.

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edit: I think I get what you are saying. I’ve just removed

df = MyFunctionReadsFromPathAndAggregations(temp.name)

part from read_file function, and return temp.name. It still does the same thing.

4

That seems unrelated to the code you posted so I cannot help with it. When I fill the missing parts in your code and run it, the body of read_file() is called only once. That is all I can say.

5

Ok thanks, I’ll dig into more to find my mistake.

6

Looks like it is was a bug. fyi.

7

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