import re  
text = "2025-12-09"  
match = re.match(r"(\d{4})-(\d{2})-(\d{2})", text)  

# 形式1：無(wú)參數(shù) → 完整匹配  
print(match.group())       # 輸出: 2025-12-09  
print(match.group(0))      # 輸出: 同上（組0代表完整匹配）  

# 形式2：整數(shù)索引 → 捕獲分組  
print(match.group(1))      # 輸出: 2025（第一個(gè)捕獲組）  
print(match.group(2))      # 輸出: 12  

# 形式3：命名組關(guān)鍵字 → 可讀性更強(qiáng)的提取  
pattern = r"(?P<year>\d{4})-(?P<month>\d{2})-(?P<day>\d{2})"  
match = re.match(pattern, text)  
print(match.group("year")) # 輸出: 2025  

pattern = r"((?:\d{4})-(\d{2}))-(\d{2})"  
match = re.match(pattern, "2025-12-09")  
print(match.group(1))  # 輸出: 2025-12（外層第一個(gè)組）  
print(match.group(2))  # 輸出: 12（內(nèi)層第二個(gè)組）  

# 解析HTTP請(qǐng)求行  
http_request = "GET /api HTTP/1.1"  
pattern = r"(?P<method>[A-Z]+) (?P<uri>\S+) (?P<protocol>HTTP/\d\.\d)"  
match = re.match(pattern, http_request)  
print(match.group("method"))  # 輸出: GET  

email = "user@example.com"  
pattern = r"(?P<local>\w+)@(?P<domain>\w+\.\w+)"  
match = re.match(pattern, email)  
if match:  
    print(f"本地部分: {match.group('local')}")  
    print(f"域名: {match.group('domain')}")  

log_line = "2025-12-09 14:30:00 [ERROR] Connection failed"  
pattern = r"(\d{4}-\d{2}-\d{2}) (\d{2}:\d{2}:\d{2}) \[(?P<level>\w+)\]"  
match = re.search(pattern, log_line)  # 注意用search而非match  
if match:  
    timestamp = match.group(1) + " " + match.group(2)  
    level = match.group("level")  
    print(f"{timestamp} - {level}")  

text = "計(jì)算(3+5)*2的結(jié)果"  
pattern = r"計(jì)算\((?P<inner>\d+[+-]\d+)\)*(?P<outer>\d+)"  
match = re.search(pattern, text)  
if match:  
    inner = match.group("inner")  # 輸出: 3+5  
    outer = match.group("outer")  # 輸出: 2  

unsafe = re.match(r"\d+", "abc")  
# 錯(cuò)誤寫(xiě)法：unsafe.group(0) → AttributeError  
if unsafe:  
    print(unsafe.group(0))  

match = re.match(r"(\d{4})", "2025")  
# 錯(cuò)誤寫(xiě)法：match.group(2) → IndexError  
# 正確：確認(rèn)組數(shù)量  
print(f"存在{match.lastindex}個(gè)捕獲組")  # 輸出: 1  

text = "<div>標(biāo)題</div><div>內(nèi)容</div>"  
# 貪婪匹配：捕獲從第一個(gè)<div>到最后一個(gè)</div>  
match = re.search(r"<div>(.*?)</div>", text)  
print(match.group(1))  # 輸出: 標(biāo)題（非貪婪模式）  

date_pattern = re.compile(r"(\d{4})-(\d{2})-(\d{2})")  
match1 = date_pattern.match("2025-12-09")  
match2 = date_pattern.match("1999-01-01")  

match = re.match(r"(\d{4})-(\d{2})", "2025-12")  
print(match.span(1))  # 輸出: (0, 4)