4 isdigit()、isnumeric()和isdecimal()的区别

unicode（=半角数字）

num = '123'
print(num.isdigit())    # True
print(num.isnumeric())  # True
print(num.isdecimal())  # True

半角与全角数字：
0-9对应Unicode编码范围：半角——’\u0030’ 到 ‘\u0039’ 全角——’\uff10’到’\uff19’
全角数字（双字节）

num = '\uff10'
print(num.isdigit())    # True
print(num.isnumeric())  # True
print(num.isdecimal())  # True

bytes数字

num = b'6'
print(num.isdigit())      # True
# print(num.isnumeric())  # 取消注释可查看错误
# AttributeError: 'bytes' object has no attribute 'isnumeric'
# print(num.isdecimal())  # 取消注释可查看错误
# AttributeError: 'bytes' object has no attribute 'isdecimal'

阿拉伯数字

num = 'Ⅱ'
print(num.isdigit())    # False
print(num.isnumeric())  # True
print(num.isdecimal())  # False

汉字数字

num = '四'
print(num.isdigit())    # False
print(num.isnumeric())  # True
print(num.isdecimal())  # False