Python - Reading and Writing Files - ファイルの読み込み、read関数、条件分岐、if文

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 10(Reading and Writing Files)、Exercise 5の解答を求めてみる。

コード

#!/usr/bin/env python3
from unittest import TestCase, main
from test.support import captured_stdout
from typing import TextIO
from io import StringIO

print('5.')


class MyTestCase(TestCase):
    def test1(self):
        in_file = StringIO('''Example
# Comment
# Comment
Data line
''')
        with captured_stdout() as stdout:
            process_file(in_file)
        self.assertEqual(stdout.getvalue(), 'Data line\n\n')

    def test2(self):
        in_file = StringIO('''Example
# Comment
# Comment
''')
        with captured_stdout() as stdout:
            process_file(in_file)
        self.assertEqual(stdout.getvalue(), '\n')


def skip_header(reader: TextIO) -> str:
    _ = reader.readline()
    line = reader.readline()
    while line.startswith('#'):
        line = reader.readline()
    return line


def process_file(reader: TextIO) -> None:
    line = skip_header(reader).strip()
    if line == '':
        print()
    else:
        print(line)
        print(reader.read())


if __name__ == "__main__":
    main()

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

% ./sample5.py -v
5.
test1 (__main__.MyTestCase) ... ok
test2 (__main__.MyTestCase) ... ok

----------------------------------------------------------------------
Ran 2 tests in 0.000s

OK
%