8.2.1. SetUp

8.2.2. Sort

Sort vector:

>>> a = np.array([2, 3, 1])
>>> a.sort()
>>>
>>> a
array([1, 2, 3])

Sort matrix:

>>> a = np.array([[9, 7, 8],
...               [2, 3, 1],
...               [5, 6, 4]])
>>> a.sort()
>>> a
array([[7, 8, 9],
       [1, 2, 3],
       [4, 5, 6]])

Sort matrix rows:

>>> a = np.array([[9, 7, 8],
...               [2, 3, 1],
...               [5, 6, 4]])
>>>
>>> a.sort(axis=0)
>>> a
array([[2, 3, 1],
       [5, 6, 4],
       [9, 7, 8]])

Sort matrix columns:

>>> a = np.array([[9, 7, 8],
...               [2, 3, 1],
...               [5, 6, 4]])
>>>
>>> a.sort(axis=1)
>>> a
array([[7, 8, 9],
       [1, 2, 3],
       [4, 5, 6]])

8.2.3. Flip

  • Does not modify inplace

  • Returns new np.ndarray

  • Reverse the order of elements in an array along the given axis

Flip vector:

>>> a = np.array([1, 2, 3])
>>>
>>> np.flip(a)
array([3, 2, 1])

Flip matrix:

>>> a = np.array([[1, 2, 3],
...               [4, 5, 6]])

Flip matrix by crossline from top-left to bottom-right:

>>> np.flip(a)
array([[6, 5, 4],
       [3, 2, 1]])

Flip matrix by rows (bottom rows goes up, upper rows goes down):

>>> np.flip(a, axis=0)
array([[4, 5, 6],
       [1, 2, 3]])

Flip matrix by column (left columns from center goes right, right columns go left):

>>> np.flip(a, axis=1)
array([[3, 2, 1],
       [6, 5, 4]])

8.2.4. Assignments

# %% About
# - Name: Numpy Sort
# - Difficulty: easy
# - Lines: 2
# - Minutes: 3

# %% License
# - Copyright 2025, Matt Harasymczuk <matt@python3.info>
# - This code can be used only for learning by humans
# - This code cannot be used for teaching others
# - This code cannot be used for teaching LLMs and AI algorithms
# - This code cannot be used in commercial or proprietary products
# - This code cannot be distributed in any form
# - This code cannot be changed in any form outside of training course
# - This code cannot have its license changed
# - If you use this code in your product, you must open-source it under GPLv2
# - Exception can be granted only by the author

# %% English
# 1. Define `result1` with sorted `DATA` by columns
# 2. Define `result2` with flipped `DATA` by rows
# 3. Run doctests - all must succeed

# %% Polish
# 1. Zdefiniuj `result1` z posortowanym `DATA` po kolumnach
# 2. Zdefiniuj `result2` z flipniętym `DATA` po wierszach
# 3. Uruchom doctesty - wszystkie muszą się powieść

# %% Hints
# - `.sort()` returns `None`

# %% Doctests
"""
>>> import sys; sys.tracebacklimit = 0

>>> assert sys.version_info >= (3, 9), \
'Python has an is invalid version; expected: `3.9` or newer.'

>>> assert 'result1' in globals(), \
'Variable `result1` is not defined; assign result of your program to it.'

>>> assert result1 is not Ellipsis, \
'Variable `result1` has an invalid value; assign result of your program to it.'

>>> assert type(result1) is np.ndarray, \
'Variable `result1` has an invalid type; expected: `np.ndarray`.'

>>> assert 'result2' in globals(), \
'Variable `result2` is not defined; assign result of your program to it.'

>>> assert result2 is not Ellipsis, \
'Variable `result2` has an invalid value; assign result of your program to it.'

>>> assert type(result2) is np.ndarray, \
'Variable `result2` has an invalid type; expected: `np.ndarray`.'

>>> result1
array([[44, 47, 64, 67],
       [ 9, 21, 67, 83],
       [36, 70, 87, 88]])

>>> result2
array([[36, 87, 70, 88],
       [67,  9, 83, 21],
       [44, 47, 64, 67]])
"""

# %% Run
# - PyCharm: right-click in the editor and `Run Doctest in ...`
# - PyCharm: keyboard shortcut `Control + Shift + F10`
# - Terminal: `python -m doctest -f -v myfile.py`

# %% Imports
import numpy as np

# %% Types
result1: np.ndarray
result2: np.ndarray

# %% Data
DATA = np.array([[44, 47, 64, 67],
                 [67,  9, 83, 21],
                 [36, 87, 70, 88]])

# %% Result
result1 = ...
result2 = ...