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

# Check if all characters in the string are digits 
S = '123'
x = S.isdigit()
print(x)
# Prints True

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

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

isdigit() on Unicode Digit Characters

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

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

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

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

isdecimal() vs isdigit() vs isnumeric()

Following examples explain the difference between the three methods.

# Is 42 a decimal or digit or numeric number?
print('42'.isdecimal())        # Prints True
print('42'.isdigit())          # Prints True
print('42'.isnumeric())        # Prints True
# Is ² (Superscript Two) a decimal or digit or numeric number?
print('\u00b2'.isdecimal())    # Prints False
print('\u00b2'.isdigit())      # Prints True
print('\u00b2'.isnumeric())    # Prints True
# Is ⅓ (Vulgar Fraction One Third) a decimal or digit or numeric number?
print('\u2153'.isdecimal())    # Prints False
print('\u2153'.isdigit())      # Prints False
print('\u2153'.isnumeric())    # Prints 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.