[Term Entry] Python NumPy - ndarray: byteswap()

content/numpy/concepts/ndarray/terms/byteswap/byteswap.md

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+---
+Title: 'byteswap()'
+Description: 'Swaps the byte order of each element in a NumPy ndarray.'
+Subjects:
+  - 'Computer Science'
+  - 'Data Science'
+Tags:
+  - 'Array'
+  - 'Data'
+  - 'NumPy'
+CatalogContent:
+  - 'learn-python-3'
+  - 'paths/data-science'
+---
+
+The **`byteswap()`** method reverses the byte order of every element in a NumPy array. This is used when converting data between systems with different endianness (byte-ordering conventions). The operation either returns a new array or modifies the original one in place when `inplace=True`.
+
+## Syntax
+
+```pseudo
+ndarray.byteswap(inplace=False)
+```
+
+**Parameters:**
+
+- `inplace` (optional): When set to `True`, the byte order of the existing array is swapped in place. When `False`, a new array with swapped bytes is returned.
+
+**Return value:**
+
+Returns a new ndarray with swapped byte order, unless `inplace=True`, in which case the original array is modified and returned.
+
+## Example 1
+
+In this example, the array's byte order is swapped to convert the data into the opposite endianness:
+
+```py
+import numpy as np
+
+arr = np.array([1, 256, 1024], dtype=np.int32)
+
+print("Original array:")
+print(arr)
+print("Original dtype:", arr.dtype)
+
+swapped = arr.byteswap()
+
+print("\nAfter byteswap():")
+print(swapped)
+print("Swapped dtype:", swapped.dtype)
+```
+
+The output of this code is:
+
+```shell
+Original array:
+[   1  256 1024]
+Original dtype: int32
+
+After byteswap():
+[16777216    65536   262144]
+Swapped dtype: int32
+```
+
+## Example 2
+
+This example demonstrates `byteswap(inplace=True)` and shows how the original data is altered directly:
+
+```py
+import numpy as np
+
+arr = np.array([100, 200, 300], dtype=np.int32)
+
+print("Before inplace byteswap:", arr)
+
+arr.byteswap(inplace=True)
+
+print("After inplace byteswap:", arr)
+```
+
+The output of this code is:
+
+```shell
+Before inplace byteswap: [100 200 300]
+After inplace byteswap: [1677721600 -939524096  738263040]
+```
+
+## Codebyte Example
+
+Use the codebyte below to inspect how `byteswap()` affects a 2-D array and observe the internal memory representation change:
+
+```codebyte/python
+import numpy as np
+
+matrix = np.array([[1, 2], [3, 4]], dtype=np.int16)
+
+print("Original:")
+print(matrix)
+
+swapped = matrix.byteswap()
+
+print("\nByteswapped:")
+print(swapped)
+```
+
+## Frequently Asked Questions
+
+### 1. What is the function of byteswap() in Python?
+
+The `byteswap()` method reverses the byte order of every element in a NumPy array. It is commonly used when preparing data for systems with different endianness or when interpreting binary data from external sources.
+
+### 2. What are bytes and bytearrays in Python?
+
+A `bytes` object in Python is an immutable sequence of byte values, while a bytearray is a mutable version of the same concept. Both store raw binary data and are often used for file handling, networking, and low-level memory operations.
+
+### 3. How to shuffle a NumPy ndarray?
+
+A NumPy array can be shuffled using `np.random.shuffle()` for in-place row-wise shuffling or `np.random.permutation()` to return a shuffled copy. These functions randomize the order of elements while preserving the array’s structure.