Common Regular Expression Metacharacters and Their Usage in Python

Today we introduce common regular expression symbols used in Python, focusing on seven ordinary metacharacters, the OR operator, escape characters, anchors (^ and $), quantifiers (.*, ?, *), and grouping parentheses.

For the ordinary metacharacters, examples show how import re str1 = "acb azb abb a6b aab" result1 = re.findall("a[a-z]b", str1) result2 = re.findall("a[0-9]b", str1) result3 = re.findall("a[za6]b", str1) print(result1) print(result2) print(result3) matches substrings where the middle character varies according to the character class.

The OR operator example demonstrates matching either "孙悟空" or "齐天大圣": import re str2 = "我是孙悟空，您可以称呼我为齐天大圣！" result1 = re.findall("孙悟空|齐天大圣", str2) print(result1) .

Escape character examples compare "\n123456" , "\n123456" (literal newline) and raw strings r"\n123456" , showing how the number of backslashes affects the match of the literal "n".

Anchor symbols ^ and $ are illustrated with re.findall("^你", str6) and re.findall("省$", str6) , matching the start or end of a string.

Quantifier examples use patterns like a.b , a*b , a?b , a.*b , and a.*?b on the string "abcdaabb" to show greedy vs. non‑greedy matching.

Grouping with parentheses is shown by extracting digits and Chinese characters: re.findall("a(\d+)b([\u4e00-\u9fa5]+)c", "a321b木头人c") returns the captured groups.

Additional sections cover shorthand character classes such as \d / \D , \s / \S , and \w / \W , each with example strings and explanations of what they match.