Regex has been useful in my work but it seems I can’t always figure things out on site without extensively going through the likes of StackOverflow. Recently I could pick up some time to read the official guide for python regex and it’s proved to be helpful.
Repetition
Three metacharacters for repetitive matching function as follows.
| Metacharacter | Equivalence | Example |
|---|---|---|
* |
{0, } | ca*t -> ct, cat, caat, … |
+ |
{1, } | ca*t -> cat, caat, … |
? |
{0, 1} | ca*t -> ct, cat |
Backslash Plague
Use r in the string definition to avoid backslash plague. Avoid excessive use of \ to escape metacharacters.
| Regular string | Raw string |
|---|---|
"ab*" |
r"ab*" |
"\\\\section" |
r"\\section" |
"\\w+\\s+\\1" |
r"\w+\s+\1" |