This article will discuss different ways to check if a string starts with one or more special characters in Python.
Table Of Content
- Check if String starts with special characters using Regex
- Check if String starts with special characters without using Regex
Check if String starts with any special character using Regex
In Python, the regex module provides a function search(str, pattern). It accepts a string and regex pattern as arguments. Then it scans through the string and looks for the given regex pattern. If a match to the pattern is found, then it returns the Match object; otherwise, it returns None. We can use this to check if a string starts with any special character or not. For that, we will use the following regex pattern,
import string pattern = r'^[' + string.punctuation + ']+'
In Python, the string module provides a variable punctuation that contains all the special characters i.e. r”””!”#$%&'()*+,-./:;<=>[email protected][]^_`{|}~”””. We used that string to create the regex pattern. This pattern checks if the string starts with one or more special characters. Let’s see some examples,
Example 1:
import re
import string
# Create a regex pattern to match a string
# that starts with one or more special characters
pattern = r'^[' + string.punctuation + ']+'
sample_str = "$sample string"
# Check if string starts with special characters
if re.search(pattern, sample_str) is not None:
print("The String starts with special characters")
else:
print("The String do not starts with special characters")
Output
The String starts with special characters
Our string has a special character at the beginning, and the regex pattern successfully detected that.
Example 2:
import re
import string
# Create a regex pattern to match a string
# that starts with one or more special characters
pattern = r'^[' + string.punctuation + ']+'
sample_str = "sample string"
# Check if string starts with special characters
if re.search(pattern, sample_str) is not None:
print("The String starts with special characters")
else:
print("The String do not starts with special characters")
Output
The String do not starts with special characters
Our string had no special character at the starting. It was a negative test.
Check if String starts with any special character without Regex
Select the string’s first character using the subscript operator i.e. str[0]. Then check if that character matches any special character in “string.punctuation”. If yes, then it means that our string starts with a special character, otherwise not. Let’s see some examples,
Example 1:
import string
sample_str = "%%sample string"
# Check if string starts with a special character
if sample_str[0] in string.punctuation:
print("The String starts with a special character")
else:
print("The String do not starts with a special character")
Output
The String starts with special characters
Our string has a special character at the beginning, and the regex pattern successfully detected that.
Example 2:
import string
sample_str = "sample string"
# Check if string starts with a special character
if sample_str[0] in string.punctuation:
print("The String starts with a special character")
else:
print("The String do not starts with a special character")
Output
The String do not starts with special characters
Our string had no special character at the starting. It was a negative test.
Summary:
We learned two different ways to check if a string starts with special characters in Python.