memoryview()

The built-in memoryview() function provides a way to access the internal data of an object that supports the buffer protocol without copying it. It’s particularly useful for efficiently manipulating large datasets or interfacing with binary data:

Python 
>>> image = bytearray([0, 127, 255, 64]) >>> mv = memoryview(image) >>> mv[0] 0

memoryview() Signature

Python Syntax 
memoryview(object)

Arguments

Argument Description
object An object supporting the buffer protocol, such as bytes, bytearray, or array.array.

Return Value

  • Returns a memoryview object, which allows for efficient access to the data without copying it.

memoryview() Examples

With a bytearray as an argument:

Python 
>>> data = bytearray(b"Hello") >>> mv = memoryview(data) >>> mv[1] = ord("a") >>> bytes(mv) b'Hallo'

With a bytes object as an argument:

Python 
>>> data = bytes(b"World") >>> mv = memoryview(data) >>> mv[0] # ASCII for W 87

memoryview() Common Use Cases

The most common use cases for the memoryview() function include:

  • Accessing and manipulating slices of large datasets without copying them
  • Interfacing with C extensions or libraries that require buffer protocol support
  • Performing efficient operations on binary data, like image processing or data serialization

memoryview() Real-World Example

Suppose you have a bytearray representing pixel data of an image, and you want to invert the pixel values efficiently. You can use the memoryview() function:

Python 
>>> image = bytearray([0, 127, 255, 64, 128, 192, 32, 96, 160]) >>> mv = memoryview(image) >>> for i in range(len(mv)): ...  mv[i] = 255 - mv[i] ... >>> list(mv) [255, 128, 0, 191, 127, 63, 223, 159, 95]

In this example, the memoryview object allows you to invert the pixel values directly, reflecting the changes on the original bytearray. This approach is memory-efficient and fast because it avoids unnecessary data copying.

Python's Built-in Functions: A Complete Exploration

Tutorial

Python's Built-in Functions: A Complete Exploration

In this tutorial, you'll learn the basics of working with Python's numerous built-in functions. You'll explore how to use these predefined functions to perform common tasks and operations, such as mathematical calculations, data type conversions, and string manipulations.

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For additional information on related topics, take a look at the following resources:

By Leodanis Pozo Ramos • Updated Jan. 17, 2025 • Reviewed by Dan Bader
Python’s Built-in Functions Share Feedback