Python 3.8 cannot run textual

[Tim-Cao]

1. Clone https://github.com/Tim-Cao/work-with-script
2. Run python3 initialization.py under root dir
3. Run python3 script.py under root dir

Actual Results

liferay@CN-9S589K3:~/Github/work-with-script$ python3 script_app.py
╭─────────────────────────────────────────────────────────────────────────────────────── Traceback (most recent call last) ───────────────────────────────────────────────────────────────────────────────────────╮
│ /home/liferay/.pyenv/versions/3.8.15/lib/python3.8/site-packages/textual/app.py:2127 in _process_messages                                                                                                       │
│                                                                                                                                                                                                                 │
│   2124 │   │                                                                                    ╭──────────────────────────────────────── locals ─────────────────────────────────────────╮                     │
│   2125 │   │   try:                                                                             │          error = StylesheetError("unable to read CSS file '/liferay/src/css/main.css'") │                     │
│   2126 │   │   │   if self.css_path:                                                            │       headless = False                                                                  │                     │
│ ❱ 2127 │   │   │   │   self.stylesheet.read_all(self.css_path)                                  │   message_hook = None                                                                   │                     │
│   2128 │   │   │   for path, css, tie_breaker, scope in self._get_default_css():                │ ready_callback = None                                                                   │                     │
│   2129 │   │   │   │   self.stylesheet.add_source(                                              │           self = ScriptApp(title='Working with Script', classes={'-dark-mode'})         │                     │
│   2130 │   │   │   │   │   css,                                                                 │  terminal_size = None                                                                   │                     │
│                                                                                                 ╰─────────────────────────────────────────────────────────────────────────────────────────╯                     │
│                                                                                                                                                                                                                 │
│ /home/liferay/.pyenv/versions/3.8.15/lib/python3.8/site-packages/textual/css/stylesheet.py:268 in read_all                                                                                                      │
│                                                                                                                                                                                                                 │
│   265 │   │   │   StylesheetParseError: If the CSS is invalid.                                 ╭───────────────────── locals ─────────────────────╮                                                             │
│   266 │   │   """                                                                              │  path = PosixPath('/liferay/src/css/main.css')   │                                                             │
│   267 │   │   for path in paths:                                                               │ paths = [PosixPath('/liferay/src/css/main.css')] │                                                             │
│ ❱ 268 │   │   │   self.read(path)                                                              │  self = <Stylesheet []>                          │                                                             │
│   269 │                                                                                        ╰──────────────────────────────────────────────────╯                                                             │
│   270 │   def has_source(self, path: str | PurePath) -> bool:                                                                                                                                                   │
│   271 │   │   """Check if the stylesheet has this CSS source already.                                                                                                                                           │
│                                                                                                                                                                                                                 │
│ /home/liferay/.pyenv/versions/3.8.15/lib/python3.8/site-packages/textual/css/stylesheet.py:253 in read                                                                                                          │
│                                                                                                                                                                                                                 │
│   250 │   │   │   │   css = css_file.read()                                                    ╭──────────────── locals ────────────────╮                                                                       │
│   251 │   │   │   path = os.path.abspath(filename)                                             │ filename = '/liferay/src/css/main.css' │                                                                       │
│   252 │   │   except Exception:                                                                │     self = <Stylesheet []>             │                                                                       │
│ ❱ 253 │   │   │   raise StylesheetError(f"unable to read CSS file {filename!r}") from None     ╰────────────────────────────────────────╯                                                                       │
│   254 │   │   self.source[str(path)] = CssSource(css, False, 0)                                                                                                                                                 │
│   255 │   │   self._require_parse = True                                                                                                                                                                        │
│   256                                                                                                                                                                                                           │
╰─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
StylesheetError: unable to read CSS file '/liferay/src/css/main.css'

[davep]

Part of Textual's CI testing is that all the unit tests are run with, and must pass with, Python versions 3.7 through to 3.12. I've seen no evidence to suggest that "Python 3.8 cannot run Textual". The error you're showing above suggests there's a problem loading the stylesheet of your application.

Given that the repo you point to seems to require a lot of dependencies and a lot of setup, that makes it tricky for someone else to test. Could I encourage you to create an MRE that demonstrates the same problem, especially one that demonstrates the claim in the subject of this discussion?

[Tim-Cao]

Hi @davep, you could use following simple example. Run the app on python 3.8
script_app.py

import os
import sys

from textual.app import App, ComposeResult
from textual.containers import *
from textual.widgets import *

root = os.path.dirname(__file__)

sys.path.append(root)


class ScriptApp(App):
    CSS_PATH = root + "/demo.css"

    def compose(self) -> ComposeResult:
        yield Header()
        with Horizontal(id="main-content"):
            yield ListView(
                ListItem(Static("Forward Failure PR", classes="nav-item"), id="nav-1"),
                ListItem(
                    Static("Create PR and Forward", classes="nav-item"), id="nav-2"
                ),
                ListItem(Static("Create TF Ticket", classes="nav-item"), id="nav-3"),
                ListItem(Static("Write Comments", classes="nav-item"), id="nav-4"),
                ListItem(Static("Write Description", classes="nav-item"), id="nav-5"),
                ListItem(Static("Trigger Gauntlet", classes="nav-item"), id="nav-6"),
            )
            with ContentSwitcher(initial="nav-1"):
                with VerticalScroll(id="nav-1"):
                    yield Label("Enter the failure pull request number: ")
                    yield Input(id="failure-pull-request-number")
                    yield Static()
                    yield Button("Submit", variant="primary", id="button-1")
        yield Footer()


app = ScriptApp()

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

demo.css

Button {
    margin-left: 1;
}

Input {
    margin-right: 1;
}

Label {
    margin-left: 1;
}

ListView {
    width: 30;
}

ListItem {
    box-sizing: content-box;
    content-align: center middle;
    color: $text;
    height: 1;
    margin-left: 1;
    margin-right: 2;
    margin-top: 1;
    margin-bottom: 1;
    padding-top: 1;
    padding-bottom: 1;
}

ListView > ListItem.--highlight {
    background: $accent;
    text-style: bold;
}

RichLog {
    border: tall $background;
    background: $boost;
    overflow-y: auto;
}

Switch {
    border: blank;
}

Switch > .switch--slider {
    background: $panel-lighten-2;
    color: white;
}

Switch.-on > .switch--slider {
    background: rgb(11,95,255);
    color: white;
}

TextArea {
    height: 20;
}

.unselected {
    display: none;
}

.unselected.visible {
    display: block;
}

#assign-to-me-label {
    height: 3;
    content-align: left middle;
    margin-left: 1;
}

#main-content {
    height: 2fr;
}

.nav-item {
    width: 30;
    text-align: center;
    padding-right: 2;
}

#switch-container {
    margin-left: 1;
    height: auto;
}

[davep]

Thanks. This isn't a problem with Textual, or with Python 3.8. You can reduce your problem down to this:

import os

root = os.path.dirname(__file__)
print(root + "/demo.css")

Your method of attempting to locate the CSS file is resulting in it looking in the root of the filesystem; this will be the case for any version of Python and doesn't involve Textual.

Moreover, Textual's CSS loading mechanism takes care of locating the CSS file. If you change the CSS declaration to this:

    CSS_PATH = "demo.css"

the code will work fine.

[Tim-Cao]

Thanks for your help @davep, it is related to python

import os

root = os.path.dirname(os.path.abspath(__file__))
print(root + "/demo.css")

Works on 3.8

[davep]

Correct, you'd need to do this with any version of Python.

[Tim-Cao]

On 3.9, 3.10 and 3.11, no need

[davep]

Ahh, yes, forgot that changed.