Why does Python detect the symbol “²” as a digit?

Question

Can someone say if "²" is a symbol or a digit? (alt+1277, power of two)

print("²".isdigit())
# True
print("²".isnumeric())
# True

Because Python says it's a digit, but it's not actually a digit. Am I wrong? Or it's a bug?

Answer 1

It is explicitly documented as a digit:

str.isdigit()

Return True if all characters in the string are digits and there is at least one character, False` otherwise. Digits include decimal characters and digits that need special handling, such as the compatibility superscript digits . This covers digits which cannot be used to form numbers in base 10, like the Kharosthi numbers. Formally, a digit is a character that has the property value Numeric_Type=Digit or Numeric_Type=Decimal.

Regarding Numeric_Type , this is defined by Unicode:

Numeric_Type=Digit

Variants of positional decimal characters (Numeric_Type=Decimal) or sequences thereof. These include super/subscripts , enclosed, or decorated by the addition of characters such as parentheses, dots, or commas.

Answer 2

Python is smart enough to tag unicode characters as digits, just because it's possible.

To complete this good answer , note that you can even get the floating point representation of the character:

>>> from unicodedata import numeric
>>> numeric("²")
2.0

It's float because there are unicode versions of 1/2, 3/2...

(see How to convert unicode numbers to ints? )