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.