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memoryview

types

Creates a view into an object's buffer without copying the data. Lets you work with slices of binary data efficiently.

Syntax

memoryview(object)

memoryview only accepts objects that support the buffer protocol — bytes, bytearray, array.array; a str or a list raises TypeError. Writing through the view works only if the underlying object is mutable: assigning into memoryview(b'...') fails because bytes is read-only. Slicing a view gives another memoryview rather than bytes (hence the bytes(...) wrapper), and while a view is alive the bytearray cannot be resized — append or extend raise BufferError.

Examples

b = bytearray(b'hello world')
mv = memoryview(b)
print(bytes(mv[6:11]))  # → b'world'
mv[0] = ord('H')
print(b)  # → bytearray(b'Hello world')
print(mv.format)  # → B (unsigned char)
print(mv.itemsize)  # → 1
print(len(mv))  # → 11

See also

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