How do I check if input string is a valid regular expression or not in Python

Question

HI all. Pretty simple question! 

Basically, in Java, I was able to use the following piece of code to check if my input string was a valid or an invalid regular expression. 

Check out the code:

boolean isRegex;
try {
  Pattern.compile(input);
  isRegex = true;
} catch (PatternSyntaxException e) {
  isRegex = false;
}

Now my question is that I want to know what the Python equivalent is of Pattern.compile() and PatternSyntaxException?

I am sure it exists in Python and that I am unaware of it. Using this in a project of mine.

All help appreciated!

Answer 1

Hi. Good question! Well, just like what we have in Java, for Python we have re.error exception just for this very purpose. Check out the code below to understand it better:

import re

try:
    re.compile('[')
    is_valid = True
except re.error:
    is_valid = False

What is re.error exception, you ask?

Here is the formal definition I got from the official documentation:

"Exception raised when a string passed to one of the functions here is not a valid regular expression or when some other error occurs during compilation or matching. "

Hope this helped! 

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Thanks!