Python String isdigit() Method

Determines whether the string contains digits

Usage

The isdigit() method returns TRUE if the string is nonempty and all characters in it are digits. Otherwise, it returns FALSE.

Unicode characters such as superscript digits ¹ , ² and ³ are also considered as digits.

Syntax

string.isdigit()

Basic Examples

Example: Check if all characters in the string are digits

S = '123'
x = S.isdigit()
print(x)    # True

Below are a few examples where isdigit() method returns false.

Example:

# floating point number
S = '123.456'
x = S.isdigit()
print(x)    # False
# number with thousands separator
S = '1,234,567'
x = S.isdigit()
print(x)    # False
# empty string
S = ''
x = S.isdigit()
print(x)    # False

isdigit() on Unicode Digit Characters

Unicode character such as superscript digit ² is considered as a digit.

Example:

S = '10²'
x = S.isdigit()
print(x)    # True

Special Unicode characters like circled digits are also considered as digits.

Example:

S = '\u2465' # Special Unicode 
x = S.isdigit()
print(S)    # True

isdecimal() vs isdigit() vs isnumeric()

Following examples explain the difference between the three methods.

Example: Is 42 a decimal or digit or numeric number?

print('42'.isdecimal())		# True
print('42'.isdigit())		# True
print('42'.isnumeric())		# True

Example: Is ² (Superscript Two) a decimal or digit or numeric number?

print('\u00b2'.isdecimal())		# False
print('\u00b2'.isdigit())		# True
print('\u00b2'.isnumeric())		# True

Example: Is ⅓ (Vulgar Fraction One Third) a decimal or digit or numeric number?

print('\u2153'.isdecimal())		# False
print('\u2153'.isdigit())		# False
print('\u2153'.isnumeric())		# True

As you can see, the main difference between the three functions is:

  • isdecimal() method supports only Decimal Numbers.
  • isdigit() method supports Decimals, Subscripts, Superscripts.
  • isnumeric() method supports Digits, Vulgar Fractions, Subscripts, Superscripts, Roman Numerals, Currency Numerators.