Python - Serialization - Big- and Little-Endian Redux - int to little-endian, int class, to_bytes method

Programming Bitcoin
Learn How to Program Bitcoin from Scratch
楽天ブックス(Kobo) 紀伊國屋書店(Kinoppy)

開発環境

• macOS Mojave - 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)

Programming Bitcoin: Learn How to Program Bitcoin from Scratch (Jimmy Song(著)、O'Reilly Media)のChapter 4(Serialization)、Big- and Little-Endian Redux、Exercises 8(86)の解答を求めてみる。

コード

Python 3

#!/usr/bin/env python3
from unittest import TestCase, main


def little_endian_to_int(b: bytes) -> int:
    return int.from_bytes(b, 'little')


def int_to_little_endian(n: int, length: int) -> bytes:
    return n.to_bytes(length, 'little')


class MyTestCase(TestCase):
    def setUp(self):
        pass

    def tearDown(self):
        pass

    def test_little_endian_to_int_1(self):
        self.assertEqual(little_endian_to_int(b'\x01\x00'), 16 ** 0 * 1)

    def test_little_endian_to_int_2(self):
        self.assertEqual(little_endian_to_int(b'\x00\x01'), 16 ** 2 * 1)

    def test_int_to_little_endian_1(self):
        self.assertEqual(b'\x01', int_to_little_endian(1, 1))

    def test_int_to_little_endian_2(self):
        self.assertEqual(b'\x00\x01', int_to_little_endian(1 * 16 ** 2, 2))

    def test_little_endian_to_int_reverse1(self):
        b = b'\x00\x01'
        self.assertEqual(b, int_to_little_endian(little_endian_to_int(b), 2))

    def test_little_endian_to_int_reverse2(self):
        b = b'\x01\x00'
        self.assertEqual(b, int_to_little_endian(little_endian_to_int(b), 2))

    def test_int_to_little_endian_reverse1(self):
        self.assertEqual(1, little_endian_to_int(int_to_little_endian(1, 1)))

    def test_int_to_little_endian_reverse2(self):
        n = 16 ** 2
        self.assertEqual(n, little_endian_to_int(int_to_little_endian(n, 2)))


if __name__ == '__main__':
    for b in [b'\x10\x00', b'\x00\x10']:
        for o in [b, little_endian_to_int(b)]:
            print(o)
        print()
    main()

入出力結果(cmd(コマンドプロンプト)、Terminal、Jupyter(IPython))

C:\Users\...>py sample8.py
b'\x10\x00'
16

b'\x00\x10'
4096

EE..
======================================================================
ERROR: test_int_to_little_endian_1 (__main__.MyTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "sample8.py", line 28, in test_int_to_little_endian_1
    self.assertEqual(int_to_little_endian(1), b'\x01')
NameError: name 'int_to_little_endian' is not defined

======================================================================
ERROR: test_int_to_little_endian_2 (__main__.MyTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "sample8.py", line 31, in test_int_to_little_endian_2
    self.assertEqual(int_to_little_endian(1 * 16 ** 2, b'\x00\x01'))
NameError: name 'int_to_little_endian' is not defined

----------------------------------------------------------------------
Ran 4 tests in 0.001s

FAILED (errors=2)
C:\Users\...>py sample8.py
b'\x10\x00'
16

b'\x00\x10'
4096

.E..
======================================================================
ERROR: test_int_to_little_endian_2 (__main__.MyTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "sample8.py", line 31, in test_int_to_little_endian_2
    self.assertEqual(int_to_little_endian(1 * 16 ** 2, b'\x00\x01'))
TypeError: int_to_little_endian() takes 1 positional argument but 2 were given

----------------------------------------------------------------------
Ran 4 tests in 0.000s

FAILED (errors=1)
C:\Users\...>py sample8.py
b'\x10\x00'
16

b'\x00\x10'
4096

....
----------------------------------------------------------------------
Ran 4 tests in 0.000s

OK

C:\Users\...>py sample8.py
b'\x10\x00'
16

b'\x00\x10'
4096

.....F
======================================================================
FAIL: test_little_endian_to_int_reverse2 (__main__.MyTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "sample8.py", line 39, in test_little_endian_to_int_reverse2
    self.assertEqual(int_to_little_endian(little_endian_to_int(b)), b)
AssertionError: b'\x01' != b'\x01\x00'

----------------------------------------------------------------------
Ran 6 tests in 0.001s

FAILED (failures=1)
C:\Users\...>py sample8.py
  File "sample8.py", line 13
    class MyTestCase(TestCase):
        ^
SyntaxError: invalid syntax
C:\Users\...>py sample8.py
b'\x10\x00'
16

b'\x00\x10'
4096

......
----------------------------------------------------------------------
Ran 6 tests in 0.000s

OK

C:\Users\...>py sample8.py
b'\x10\x00'
16

b'\x00\x10'
4096

.......
----------------------------------------------------------------------
Ran 7 tests in 0.000s

OK

C:\Users\...>py sample8.py
b'\x10\x00'
16

b'\x00\x10'
4096

........
----------------------------------------------------------------------
Ran 8 tests in 0.000s

OK

C:\Users\...>py sample8.py -v
b'\x10\x00'
16

b'\x00\x10'
4096

test_int_to_little_endian_1 (__main__.MyTestCase) ... ok
test_int_to_little_endian_2 (__main__.MyTestCase) ... ok
test_int_to_little_endian_reverse1 (__main__.MyTestCase) ... ok
test_int_to_little_endian_reverse2 (__main__.MyTestCase) ... ok
test_little_endian_to_int_1 (__main__.MyTestCase) ... ok
test_little_endian_to_int_2 (__main__.MyTestCase) ... ok
test_little_endian_to_int_reverse1 (__main__.MyTestCase) ... ok
test_little_endian_to_int_reverse2 (__main__.MyTestCase) ... ok

----------------------------------------------------------------------
Ran 8 tests in 0.001s

OK

C:\Users\...>