Streamlit run myapp.py is not writing the files in the project folder but running the code from python is

[giacomo]

Summary

These functions are downloading mutiple zipfiles from an ftp server, extract the files and saving them in the project folder (where the myapp.py is).

If I run the code directly in python it works and the files are written in the project folder but if I do it on my streamlit app the code will run but the folder stays empty. There are no error messages.

I am on windows and I am running the latest version of streamlit.

Steps to reproduce

Code snippet:

@st.cache_data
def download_and_unzip(url, extract_to='.'):
    http_response = urlopen(url)
    zipfile = ZipFile(BytesIO(http_response.read()))
    zipfile.extractall(path=extract_to)

@st.cache_data
def get_storm_data():
    # unzip all files
    for zip_file in nhc_urls_list:
        url_zip_file = url + zip_file
        print("Downloading: " + url_zip_file)
        download_and_unzip(url_zip_file)

[mathcatsand]

I’m not sure I understand. You have a caching decorator on functions that return no values. The purpose of caching to to save the return value of a function. If you have side effects–things being written to the screen or to a file–then you will not want to cache that function. Caching does not have any memory of the internals of a function, only the return value. The return value of those two function is None and that’s all caching knows (and cares about).