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?
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.
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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 –
- Python – Check If a Character Appears Twice in String
- Python – Check If String Contains Vowels
- Python – Check If String Contains Lowercase Letters
- Python – Check If String Contains Uppercase Letters
- Python String Uppercase – With Examples
- Python String Lowercase – With Examples
- Python – Capitalize First Letter of Each Word
- Python – Check If All Characters in String are Same
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