capture_print does not capture stdout from system calls

[pthebaul]

Outputs from os.system or subprocess.call are not captured by textual, and appear at the top-left of the terminal instead.

My goal is to run scripts upon button presses, and to see the scripts' outputs in a Log widget in realtime.

textual diagnose didn't recognize my terminal. I am using Windows Terminal version 1.21.2911.0, but I have the same issue using the legacy terminal (by selecting "Windows Console Host" in Windows 11 settings). The issue is there using PowerShell 7.4.6 or MS-DOS for the terminal. Note that os.system runs MS-DOS.

Here is a video, and the MRE can be found below.

https://github.com/user-attachments/assets/92c3a4e4-1b40-4476-8e4f-6d591d71f5ef

from textual.app import App
from textual.widgets import Log
import os

class MyApp(App):
    def compose(self):
        yield Log(id="log")

    def on_print(self, event):
        self.query_one("#log", Log).write(event.text)

    def on_key(self, event):
        if event.key == 'q':
            print('q was pressed')
        elif event.key == 'w':
            os.system("echo w was pressed")

    def on_ready(self):
        self.begin_capture_print(self, True, True)

if __name__ == "__main__":
    app = MyApp()
    app.run()

Textual Diagnostics

Versions

Name	Value
Textual	0.85.2
Rich	13.9.3

Python

Name	Value
Version	3.12.5
Implementation	CPython
Compiler	MSC v.1940 64 bit (AMD64)
Executable	C:\Program Files\Python312\python.exe

Operating System

Name	Value
System	Windows
Release	11
Version	10.0.22631

Terminal

Name	Value
Terminal Application	Unknown
TERM	Not set
COLORTERM	Not set
FORCE_COLOR	Not set
NO_COLOR	Not set

Rich Console options

Name	Value
size	width=120, height=30
legacy_windows	False
min_width	1
max_width	120
is_terminal	True
encoding	utf-8
max_height	30
justify	None
overflow	None
no_wrap	False
highlight	None
markup	None
height	None

[github-actions[bot]]

We found the following entries in the FAQ which you may find helpful:

• No widget called TextLog
• Why doesn't Textual look good on macOS?
• How do I center a widget in a screen?

Feel free to close this issue if you found an answer in the FAQ. Otherwise, please give us a little time to review.

This is an automated reply, generated by FAQtory

[willmcgugan]

This is expected. Rich can only capture output generated from its own process. To capture output from another process, you will need to use subprocesses. There is good support for subprocesses in the standard library.

[github-actions[bot]]

Don't forget to star the repository!

Follow @textualizeio for Textual updates.

[pthebaul]

Alright, thanks for your quick reply, and thank you very much for Textual!