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python中str函式isdigit、isdecimal、isnumeric的區別

Python字串》中講了三種方法的大致用法,尚未細緻區分細節差別。
找點資料暫存,估計以後能用上。
num = "1"  #unicode
num.isdigit()   # True
num.isdecimal() # True
num.isnumeric() # True

num = "1" # 全形
num.isdigit()   # True
num.isdecimal() # True
num.isnumeric() # True

num = b"1" # byte
num.isdigit()   # True
num.isdecimal() # AttributeError 'bytes' object has no attribute 'isdecimal'
num.isnumeric() # AttributeError 'bytes' object has no attribute 'isnumeric'

num = "IV" # 羅馬數字
num.isdigit()   # True
num.isdecimal() # False
num.isnumeric() # True

num = "四" # 漢字
num.isdigit()   # False
num.isdecimal() # False
num.isnumeric() # True

===================
isdigit()
True: Unicode數字,byte數字(單位元組),全形數字(雙位元組),羅馬數字 False: 漢字數字 Error: 無 isdecimal() True: Unicode數字,,全形數字(雙位元組) False: 羅馬數字,漢字數字 Error: byte數字(單位元組) isnumeric() True: Unicode數字,全形數字(雙位元組),羅馬數字,漢字數字 False: 無 Error: byte數字(單位元組) ================ import unicodedata unicodedata.digit("2") # 2 unicodedata.decimal("2") # 2 unicodedata.numeric("2") # 2.0 unicodedata.digit("2") # 2 unicodedata.decimal("2") # 2 unicodedata.numeric("2") # 2.0 unicodedata.digit(b"3") # TypeError: must be str, not bytes unicodedata.decimal(b"3") # TypeError: must be str, not bytes unicodedata.numeric(b"3") # TypeError: must be str, not bytes unicodedata.digit("Ⅷ") # ValueError: not a digit unicodedata.decimal("Ⅷ") # ValueError: not a decimal unicodedata.numeric("Ⅷ") # 8.0 unicodedata.digit("四") # ValueError: not a digit unicodedata.decimal("四") # ValueError: not a decimal unicodedata.numeric("四") # 4.0 #"〇","零","一","壱","二","弐","三","參","四","五","六","七","八","九","十","廿","卅","卌","百","千","萬","萬","億"