RustPython/RustPython · error · ValueError

getbuffer on closed file

Error message

getbuffer on closed file

What it means

BytesIO.getbuffer (Lib/_pyio.py:907) raises ValueError('getbuffer on closed file') when called after close(). The method returns a writable memoryview over the internal bytearray; once close() has cleared that bytearray the view is impossible to produce, so the guard fires instead of returning an empty view. Unlike getvalue(), a successfully obtained buffer is also invalidated once the BytesIO closes.

Source

Thrown at Lib/_pyio.py:907

        self._pos = 0

    def __getstate__(self):
        if self.closed:
            raise ValueError("__getstate__ on closed file")
        return self.__dict__.copy()

    def getvalue(self):
        """Return the bytes value (contents) of the buffer
        """
        if self.closed:
            raise ValueError("getvalue on closed file")
        return bytes(self._buffer)

    def getbuffer(self):
        """Return a readable and writable view of the buffer.
        """
        if self.closed:
            raise ValueError("getbuffer on closed file")
        return memoryview(self._buffer)

    def close(self):
        if self._buffer is not None:
            self._buffer.clear()
        super().close()

    def read(self, size=-1):
        if self.closed:
            raise ValueError("read from closed file")
        if size is None:
            size = -1
        else:
            try:
                size_index = size.__index__
            except AttributeError:
                raise TypeError(f"{size!r} is not an integer")
            else:

View on GitHub (pinned to aaeab4f754)

Solutions

1. Obtain the memoryview while the BytesIO is open and finish using it before close()
2. If you only need the bytes, use getvalue() before closing and keep the bytes object
3. Don't close the BytesIO while any memoryview from getbuffer() is still alive

Example fix

// before
buf = io.BytesIO(b"abc")
buf.close()
view = buf.getbuffer()  # ValueError: getbuffer on closed file

// after
buf = io.BytesIO(b"abc")
view = buf.getbuffer()
data = bytes(view)  # consume while open
buf.close()

view = buf.getbuffer() if not buf.closed else memoryview(b"")

try:
    view = buf.getbuffer()
except ValueError as e:
    if "getbuffer on closed file" in str(e):
        view = memoryview(b"")
    else:
        raise

When it happens

Trigger: buf.close() followed by buf.getbuffer(); taking the memoryview inside a with-block but dereferencing/slicing it after exit; resize helpers that grab getbuffer() after cleanup closed the buffer.

Common situations: Zero-copy handoff of in-memory payloads to numpy or C extensions; slicing the buffer view in later processing stages after the owning BytesIO was closed; test teardown closing fixtures while views are still used.

Related errors

• __getstate__ on closed file
• getvalue on closed file
• read from closed file
• write to closed file
• seek on closed file

AI-assisted analysis of RustPython/RustPython@aaeab4f754 (2026-08-17). Data as JSON: /api/errors/20cf499037fb0b24. Report an issue: GitHub.