I'm currently using a regex pattern to check if a string represents a float. The pattern I'm using is `^-?(d+.d*|d*.d+)$`, which successfully matches examples like `-90.`, `.67`, and `42.6`. However, it fails for inputs like `.` and `-.`. I'm looking for suggestions to refine this regex so that it handles both cases of digits before and/or after the decimal point while ensuring there's at least one digit present in the string.
5 Answers
Your regex is quite readable! Another pattern could be `^-?d*(d.|.d)d*$`, which still adheres to the float definition with some flexibility.
Instead of using regex, you might consider directly converting the string to a float and handling any exceptions that arise. This way, you can cover edge cases without complex patterns. In some languages, there's a `TryParse()` method available, which can avoid exceptions entirely by returning a boolean to indicate success or failure, along with the result if successful. This might be a cleaner approach for data cleaning before passing to another system.
You've got a solid start, but to fully meet your needs, keep in mind that a float can start with a `+`, and it may also include exponential notation, such as `+1.21E-6`. Some programming languages will also consider integers like `10` as valid floats, even though they lack a decimal point.
Just a heads-up, your regex will match cases like `005.12`, which is technically correct but not how most people format floats. It might also accept something like `2.`, which is unusual and could indicate a data entry error.
Your regex isn't bad! Just remember that regex varieties can differ, and there are many ways to define what a float is. For example, your initial regex won't match scientific notation like `1.3e3` or `1.3e-3`. You might want to keep that in mind depending on your requirements.
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