Pythonでstrを拡張したクラスを作る。

Since __init__ is called after the object is constructed, it is too late to modify the value for immutable types. Note that __new__ is a classmethod, so I have called the first parameter cls

code:py

class Superstr(str):

def __new__(cls, sentence):

if not sentence.endswith(','):

sentence += ','

return super().__new__(cls, sentence)

# 使用例

s = Superstr("Hello")

print(s) # 出力: Hello,

s = Superstr("Hello,")

print(s) # 出力: Hello,