Forward stdout to some widget

Problem

I tried to use streamlit for the interactive clustering app. In my case clustering is long. And the only way to see any progress is to use verbose=1. In such a case, sklearn algorithm put some information to stdout. But I see no possibility to show this information with streamlit.

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[schaumb]

I created a gist from this problem https://gist.github.com/schaumb/037f139035d93cff3ad9f4f7e5f739ce with a simplified syntax, and with realtime output:

from streamlit.redirect as rd

with rd.stdout:
  print('blablabla')
  time.sleep(1)
  print('Hello from code block')

It can be configure easily:

st.sidebar.text("Standard output message here:")
to_out = st.sidebar.empty()
...
with rd.stdout(to=to_out, format='markdown'):
  print('**Hello** from markdown')

It can be nesting:

garbage = st.empty()

with rd.stdout:
  print('important message')
  with rd.stdout(to=garbage):
    print("some garbage")
  garbage.write()
  print("another important message")

What do you think?

[jesserobertson]

I built on zblz’s workaround and turned it into a wrapper that might be useful for some people:

import contextlib
from functools import wraps
from io import StringIO

import streamlit as st

def capture_output(func):
    """Capture output from running a function and write using streamlit."""

    @wraps(func)
    def wrapper(*args, **kwargs):
        # Redirect output to string buffers
        stdout, stderr = StringIO(), StringIO()
        try:
            with contextlib.redirect_stdout(stdout), contextlib.redirect_stderr(stderr):
                return func(*args, **kwargs)
        except Exception as err:
            st.write(f"Failure while executing: {err}")
        finally:
            if _stdout := stdout.getvalue():
                st.write("Execution stdout:")
                st.code(_stdout)
            if _stderr := stderr.getvalue():
                st.write("Execution stderr:")
                st.code(_stderr)

    return wrapper

Then you can do something like

stprint = capture_output(print)

stprint(some_variables)

which makes print debugging easier

edit: added relevant import statements for code snippet