Simon Willison’s Weblog

The surprising way to save memory with BytesIO (via) Itamar Turner-Trauring explains that if you have a BytesIO object in Python calling .read() on it will create a full copy of that object, doubling the amount of memory used - but calling .getvalue() returns a bytes object that uses no additional memory, instead using copy-on-write.

.getbuffer() is another memory-efficient option but it returns a memoryview which has less methods than the bytes you get back from .getvalue()- it doesn't have .find() for example.