Python - Repeating Code Using Loops - remove the negative numbers from the list, del, while loop, if statement

Practical Programming
楽天ブックス 紀伊国屋書店

開発環境

• macOS Catalina - Apple (OS)
• Emacs (Text Editor)
• Windows 10 Pro (OS)
• Visual Studio Code (Text Editor)
• Python 3.7 (プログラミング言語)

Practical Programming: An Introduction to Computer Science Using Python 3.6 (Paul Gries(著)、Jennifer Campbell(著)、Jason Montojo(著)、Pragmatic Bookshelf)のChapter 9(Repeating Code Using Loops)、Exercise 12の解答を求めてみる。

コード

#!/usr/bin/env python3
import doctest
from typing import List

print('12.')


def remove_neg(num_list: List[float]) -> None:
    """
    >>> numbers = [-5, 1, -3, 2]
    >>> remove_neg(numbers)
    >>> numbers
    [1, 2]
    >>> numbers = [1, 2, 3, -3, 6, -1, -3, 1]
    >>> remove_neg(numbers)
    >>> numbers
    [1, 2, 3, 6, 1]
    """
    i: int = 0
    while i < len(num_list):
        if num_list[i] < 0:
            del num_list[i]
        else:
            i += 1


if __name__ == '__main__':
    doctest.testmod()

入出力結果(Zsh、PowerShell、Terminal、Jupyter(IPython))

% ./sample12.py 
12.
**********************************************************************
File "./sample12.py", line 16, in __main__.remove_neg
Failed example:
    numbers
Expected:
    [1, 2, 3, 6, 1]
Got:
    [1, 2, 3, 6, -3, 1]
**********************************************************************
1 items had failures:
   1 of   6 in __main__.remove_neg
***Test Failed*** 1 failures.
% ./sample12.py 
12.
% ./sample12.py -v
12.
Trying:
    numbers = [-5, 1, -3, 2]
Expecting nothing
ok
Trying:
    remove_neg(numbers)
Expecting nothing
ok
Trying:
    numbers
Expecting:
    [1, 2]
ok
Trying:
    numbers = [1, 2, 3, -3, 6, -1, -3, 1]
Expecting nothing
ok
Trying:
    remove_neg(numbers)
Expecting nothing
ok
Trying:
    numbers
Expecting:
    [1, 2, 3, 6, 1]
ok
1 items had no tests:
    __main__
1 items passed all tests:
   6 tests in __main__.remove_neg
6 tests in 2 items.
6 passed and 0 failed.
Test passed.
%