Regex: Using lookahead assertion to check if character exist at most a certain number of times

Question

How do I use lookahead assertion to determine if a certain character exist at most a certain number of times in a string.

For example, let's say I want to check a string that has at least one character to make sure that it contains "@" at most 2 times. Thanks in advance. Using python if that matters.

Answer 1

There are lots of ways to do this, for example:

/^(?=([^@]*@){,2}[^@]*$)./