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Regular Expressions

Regular expressions are powerful tools for pattern matching and text processing. They are represented as a pattern that consists of a special set of characters to search for in a string str. The regex module needs to be imported before use.

This page provides syntax for regular expressions in Python . Each section includes an example to demonstrate the described methods.

Functions

Action

Function

Character Class

Character class specifies a list of characters to match ([...] where ... represents the list) or not match ([^...])

Anchors

Anchors are special characters that can be used to match a pattern at a specified position

Repetition and Quantifier Characters

Repetition or quantifier characters specify the number of times to match a particular character or set of characters

Input:

# regex.jl
number1 = "(555)123-4567"
number2 = "123-45-6789"

# check if matches
if occursin(r"\([0-9]{3}\)[0-9]{3}-[0-9]{4}", number1)
   println("match!")
end

if occursin(r"\([0-9]{3}\)[0-9]{3}-[0-9]{4}", number2)
  println("match!")
else
  println("no match!")
end

# capture matches
# use parentheses to "capture" different parts of a regular 
# expression for later use the first set of parentheses corresponds 
# to index 1, second to index 2, etc.

number_details = match(r"\(([0-9]{3})\)([0-9]{3}-[0-9]{4})", number1)

if number_details != nothing
   area_code = number_details[1]
   phone_number = number_details[2]

   println("area code: $area_code")
   println("phone number: $phone_number")
end

Output:

match!
no match!
area code: 555
phone number: 123-4567

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