Textualize/textual · error · StylesheetError

unable to read CSS file

Error message

unable to read CSS file {filename!r}

What it means

Stylesheet.read raises StylesheetError when the CSS file cannot be opened or read (missing file, permission error, decode error). The original exception is suppressed with 'from None'.

Solutions

1. Check CSS_PATH spelling and make it relative to __file__ using Path(__file__).parent
2. Use absolute paths or pathlib to build the CSS path
3. Ensure the .tcss/.css file is included in package data when shipping

Example fix

# before
CSS_PATH = "style.tcss"  # resolved against CWD
# after
CSS_PATH = Path(__file__) / "style.tcss"

from pathlib import Path
p = Path(__file__).parent / "style.tcss"
if not p.is_file():
    raise FileNotFoundError(p)

from textual.css.stylesheet import StylesheetError
try:
    ss.read(css_path)
except StylesheetError:
    ss.read(DEFAULT_CSS_PATH)  # fallback theme

When it happens

Trigger: Stylesheet.read('theme.tcss') where the path doesn't exist, lacks read permissions, or is not UTF-8. Also triggered by app-level CSS_PATH pointing at a nonexistent file.

Common situations: Wrong CSS_PATH relative to the app file, files not packaged in a distribution/wheel, permission issues, or paths containing '~' expansion problems (expanduser is applied, but relative paths resolve against CWD).

Related errors

• DeclarationError(name, token, message)
• failed to parse css;
• StylesheetErrors(css_rules) (renderable summarizing CSS…
• cannot mix 'none' with other style flags
• DeclarationError(error.name, error.token, error.message)

AI-assisted analysis of Textualize/textual@06dbeef4bb (2026-08-27). Data as JSON: /api/errors/9f0c555ce032be6a. Report an issue: GitHub.

Appendix: source

Thrown at src/textual/css/stylesheet.py:304

        return rules

    def read(self, filename: str | PurePath) -> None:
        """Read Textual CSS file.

        Args:
            filename: Filename of CSS.

        Raises:
            StylesheetError: If the CSS could not be read.
            StylesheetParseError: If the CSS is invalid.
        """
        filename = os.path.expanduser(filename)
        try:
            with open(filename, "rt", encoding="utf-8") as css_file:
                css = css_file.read()
            path = os.path.abspath(filename)
        except Exception:
            raise StylesheetError(f"unable to read CSS file {filename!r}") from None
        self.source[(str(path), "")] = CssSource(css, False, 0)
        self._require_parse = True

    def read_all(self, paths: Sequence[PurePath]) -> None:
        """Read multiple CSS files, in order.

        Args:
            paths: The paths of the CSS files to read, in order.

        Raises:
            StylesheetError: If the CSS could not be read.
            StylesheetParseError: If the CSS is invalid.
        """
        for path in paths:
            self.read(path)

    def has_source(self, path: str, class_var: str = "") -> bool:
        """Check if the stylesheet has this CSS source already.

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