Regular Expressions

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Regular expressions are used for matching text.
You can test regular expressions online at [1].

Syntax

Letters

[a-zA-Z]

Numbers

You should match numbers using [0-9].
\d will match unicode characters which are classified as digits.
See \d vs 0-9

Useful Regular Expressions

Mostly copied from Regex DB.

Floating Point Number

Without matching scientific notation (e.g. 1.5e-6). Reference

[-+]?[0-9]*\.?[0-9]+

With matching scientific notation (e.g. 1.5e-6). Reference
Capturing significand and exponent separately.

([-+]?[0-9]*\.?[0-9]+)(?:[eE]([-+]?[0-9]+))?

Capturing the entire string together.

([-+]?[0-9]*\.?[0-9]+(?:[eE][-+]?[0-9]+)?)