matplotlib/matplotlib · error · ValueError

Failed to parse {path} as Postscript encoding

Error message

Failed to parse {path} as Postscript encoding

What it means

Error "Failed to parse {path} as Postscript encoding" thrown in matplotlib/matplotlib.

Source

Thrown at lib/matplotlib/dviread.py:1248

    The format supported by this function is a tiny subset of PostScript.

    Parameters
    ----------
    path : `os.PathLike`

    Returns
    -------
    list
        The nth list item is the PostScript glyph name of the nth glyph.
    """
    no_comments = re.sub("%.*", "", Path(path).read_text(encoding="ascii"))
    array = re.search(r"(?s)\[(.*)\]", no_comments).group(1)
    lines = [line for line in array.split() if line]
    if all(line.startswith("/") for line in lines):
        return [line[1:] for line in lines]
    else:
        raise ValueError(f"Failed to parse {path} as Postscript encoding")


class _LuatexKpsewhich:
    @cache  # A singleton.
    def __new__(cls):
        self = object.__new__(cls)
        self._proc = self._new_proc()
        return self

    def _new_proc(self):
        return subprocess.Popen(
            ["luatex", "--luaonly", str(cbook._get_data_path("kpsewhich.lua"))],
            # mktexpk logs to stderr; suppress that.
            stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.DEVNULL,
            # Store generated pk fonts in our own cache.
            env={"MT_VARTEXFONTS": str(Path(mpl.get_cachedir(), "vartexfonts")),
                 **os.environ})

View on GitHub (pinned to b379c1b69e)

When it happens

Trigger: Thrown at lib/matplotlib/dviread.py:1248 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

AI-assisted analysis of matplotlib/matplotlib@b379c1b69e (2026-08-21). Data as JSON: /api/errors/395e6674a5aa0778. Report an issue: GitHub.