BufferError

BufferError

BufferError: Existing exports of data: object cannot be re-sized

Traceback

terminal

Traceback (most recent call last):
  File "main.py", line 3, in <module>
    data.extend(b" world")  # BufferError
BufferError: Existing exports of data: object cannot be re-sized

What causes this error

A buffer-related operation cannot proceed because the buffer is being used by another object (like a memoryview). Resizing or modifying buffer memory while exported is not allowed.

How to fix it

Release all memoryviews and buffer exports before resizing the underlying object. Delete memoryview references or let them go out of scope. Copy the data if you need to keep the view.

Code that causes this error

Broken

data = bytearray(b"hello")
view = memoryview(data)
data.extend(b" world")  # BufferError

Fixed code

Fixed

data = bytearray(b"hello")
view = memoryview(data)
del view  # release the memoryview first
data.extend(b" world")

About BufferError

A BufferError is raised when a buffer-related operation fails. This is a relatively uncommon exception that appears when working with the buffer protocol — Python's mechanism for allowing objects to share memory without copying. The most frequent scenario is trying to resize a bytearray or similar object while a memoryview is still referencing it.

Since the memoryview points directly at the underlying memory, resizing could invalidate the pointer, so Python prevents it. This error also appears in some C extensions and numpy operations when buffer conflicts occur. To resolve it, release the memoryview (by deleting it or letting it go out of scope) before modifying the underlying buffer.

In numerical computing, this can happen when multiple numpy arrays share the same memory through views.

Common scenarios

Infinite recursion from missing or incorrect base cases

Modifying dictionaries or sets during iteration

Calling generators or coroutines in unsupported ways

Using asyncio event loops incorrectly or attempting to nest them