> ## Documentation Index > Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt > Use this file to discover all available pages before exploring further. # Python memoryview A `memoryview` is a built-in Python object that exposes the C-level buffer interface of another object. It provides zero-copy access to an object's internal data, allowing developers to read and modify contiguous memory arrays (such as `bytes`, `bytearray`, or `array.array`) directly without triggering memory reallocation or creating intermediate copies. ## Syntax ```python theme={"dark"} view = memoryview(obj) ``` The `obj` passed to the constructor must support the Python buffer protocol. ## Core Mechanics **Zero-Copy Slicing** When you slice a standard Python byte string, Python allocates new memory and copies the data. When you slice a `memoryview`, Python returns a new `memoryview` instance that points to the specified offset of the original memory buffer. ```python theme={"dark"} data = b'abcdefgh' view = memoryview(data) # Creates a new view of the same memory; no data is copied slice_view = view[2:6] ``` **Mutability** A `memoryview` inherits the mutability of its underlying object. If the target object is immutable (e.g., `bytes`), the view is read-only. If the target object is mutable (e.g., `bytearray`), the view allows in-place memory modification. ```python theme={"dark"} mutable_data = bytearray(b'hello') view = memoryview(mutable_data) # Modifies the underlying bytearray directly view[0] = 74 # ASCII for 'J' print(mutable_data) # Output: bytearray(b'Jello') ``` ## Key Attributes A `memoryview` exposes several attributes that describe the underlying C array: * `obj`: The original object the view is pointing to. * `nbytes`: The total number of bytes the view represents. * `readonly`: A boolean indicating whether the underlying buffer can be modified. * `format`: A string indicating the C-type of the elements, using `struct` module syntax (e.g., `'B'` for unsigned char). * `itemsize`: The size in bytes of each element. * `shape`: A tuple indicating the length of the array in each dimension. * `strides`: A tuple indicating the number of bytes to skip to access the next element in each dimension. ## Casting Memory Layouts The `cast()` method allows you to reinterpret the underlying memory bytes as a different data type or shape without copying the data. This is strictly a reinterpretation of the C-level bytes. ```python theme={"dark"} import array # Array of 16-bit signed integers ('h') arr = array.array('h', [1000, 2000, 3000]) view = memoryview(arr) # Cast the 16-bit integer view to an 8-bit unsigned byte view ('B') byte_view = view.cast('B') ``` ## Buffer Management Because a `memoryview` holds a reference to the underlying object's buffer, it prevents the object from being resized or garbage-collected. The `release()` method explicitly releases the buffer, invalidating the view and freeing the lock on the underlying object. ```python theme={"dark"} view = memoryview(b'data') view.release() # Accessing view after release() raises a ValueError ``` Alternatively, `memoryview` supports the context manager protocol to handle buffer release automatically: ```python theme={"dark"} with memoryview(b'data') as view: length = len(view) # Buffer is automatically released when the block exits ```

Tired of Poor Python Skills? Fix That With Deep Grasping! Learn More