Master Python Regex: Understanding Special Characters and Their Uses

Today we share the last special character in regular expressions, "\d", with a detailed tutorial.

1. The special character "\d" is commonly used to represent digits. Example code is shown in the image.

The "+" symbol means one or more repetitions, representing consecutive digits. However, only "4" is output due to greedy mode, as mentioned in the previous article.

2. To match "2004", you need to add the special character "?" to make it non‑greedy, as shown in the image.

In non‑greedy mode, matching proceeds from left to right, capturing consecutive digits, resulting in "2004".

3. Another common usage is using curly braces to specify the length of the matched number, e.g., {4} for exactly four consecutive digits.

We briefly review ten common regex special characters without detailed expansion. ^: anchors the start of a string. *: matches the preceding element zero or more times. .: matches any character. $: anchors the end of a string. ?: makes the preceding quantifier non‑greedy. +: matches one or more repetitions (at least one). {2}, {2,}, {2,5}: specify exact, minimum, or range repetitions. |: logical OR between alternatives. [], [A-Za-z0-9], [^]: character classes, ranges, and negation. \s and \S: match whitespace and non‑whitespace respectively. \w and \W: match word characters (letters, digits, underscore) and their complement. [\u4E00-\u9FA5]: matches Chinese characters. (): groups for capturing substrings.