Skip to Content

Python – Check If String starts with a Number

In this tutorial, we will look at how to check if a string in Python starts with a number (digit) or not with the help of some examples.

How to check if a string starts with a numeric character?

check if a string in python starts with a number

To check if a string in Python starts with a number or not, check if the first character in the string is a digit or not using the string isdigit() function.

The built-in string isdigit() function in Python takes a string and returns True if all the characters in the string are numeric characters and there is at least one character in the string. It returns False otherwise.

So, use the string isdigit() function to check if the first character in the string (character at index 0) is a digit. The following is the syntax –

# check if string starts with a number
s[0].isdigit()

It returns True if the string starts with a numeric character.

Examples

Let’s now look at some examples. First, we will create some strings that we will use throughout this tutorial.

# create strings
s1 = "7eleven"
s2 = "apple"
s3 = "$500"
s4 = ""

# display the strings
print(s1)
print(s2)
print(s3)
print(s4)

Output:

7eleven
apple
$500

Here, we created four strings – s1, s2, s3 and s4. The string s1 starts with a digit, the string s2 starts with an alphabet, the string s3 starts with the special character '$' and the string s4 is an empty string.

Let’s now check if the strings s1, s2, and s3 start with a digit or not.

# check if string starts wtih a number
print(s1[0].isdigit())
print(s2[0].isdigit())
print(s3[0].isdigit())

Output:

True
False
False

We get True for s1 as it does start with a digit. We get False for s2 and s3 as they do not start with a digit.

Now let’s apply the above method to the empty string, s4.

# check if string starts wtih a number
print(s4[0].isdigit())

Output:

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
Input In [3], in <module>
      1 # check if string starts wtih a number
----> 2 print(s4[0].isdigit())

IndexError: string index out of range

We get an IndexError because we’re trying to access an index that does not exist (an empty string does not have a 0 index).

To avoid the above error, you can first check whether the string is non-empty and then proceed to check if the first character is a digit or not. See the example below –

# function to check if string starts wtih a digit
def check_str_starts_with_digit(s):
    if s and s[0].isdigit():
        return True
    else:
        return False

# check if string starts wtih a number
print(check_str_starts_with_digit(s4))

Output:

False

We get False as the output for the empty string.

You might also be interested in –


Subscribe to our newsletter for more informative guides and tutorials.
We do not spam and you can opt out any time.


Author

  • Piyush

    Piyush is a data scientist passionate about using data to understand things better and make informed decisions. In the past, he's worked as a Data Scientist for ZS and holds an engineering degree from IIT Roorkee. His hobbies include watching cricket, reading, and working on side projects.