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[py2rb] 抽象基底クラス

Last updated at Posted at 2022-01-31

はじめに

移植やってます。
( from python 3.7 to ruby 2.7 )

抽象基底クラス (Python)

from collections.abc import Sized

print(isinstance([1, 2], Sized))
print(issubclass(list, Sized))
print(isinstance([], Sized))
print(isinstance(set({1, 2}), Sized))
print(isinstance(3, Sized))
print(isinstance('Hello, world!', Sized))
print(isinstance({'id': 1, 'name': 'John'}, Sized))

# output
True
True 
True 
True 
False
True 
True 

こちらの記事が分かりやすい。

defined? (Ruby)

require 'set'

def sizeable(obj)
  if obj.is_a?(Integer)
    false
  else
    begin
      obj.size
      true
    rescue => exception
      obj.method_defined? :size, true
    end
  end
end

puts sizeable(3)
puts sizeable([])
puts sizeable([1, 2])
puts sizeable(Set.new([1, 2]))
puts sizeable({'id': 1, 'name': 'John'})
puts sizeable('Hello, world!')
puts sizeable(Array)
puts sizeable(Class)

# output
false
true 
true 
true 
true 
true 
true 
false

Integer.sizeってバイト数を返すんですね。

花より団子で。

メモ

  • Python の 抽象基底クラス を学習した
  • 百里を行く者は九十里を半ばとす
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