How to use FileUpload widget in jupyter lab?

For me it worked after

pip install jupyterlab-widgets
jupyter labextension install @jupyter-widgets/jupyterlab-manager

Also see

https://developer.aliyun.com/mirror/npm/package/@jupyter-widgets/jupyterlab-manager

Usage

from ipywidgets import FileUpload
from IPython.display import display
upload = FileUpload(accept='.txt', multiple=True)
display(upload)

---

with open('z_merged_output.txt', 'wb') as output_file: 
    for uploaded_filename in upload.value:
        content = upload.value[uploaded_filename]['content']   
        output_file.write(content) 

If you're using jupyterlab out the box, it doesn't have ipywidgets enabled by default, you need to rebuild it after enabling the extension. Follow the steps from here:

1. Install nodeJS
2. pip install ipywidgets
3. jupyter nbextension enable --py widgetsnbextension
4. jupyter labextension install @jupyter-widgets/jupyterlab-manager
5. (may need to restart your lab)

It says that newer Jupyterlab has it enabled, but I still had troubles with it, depending on the platform. Manual install is usually the way to go.