Python正则匹配IP时因部分匹配致索引-1结果错误的修复方法

问题背景 #

编写的Python代码意图从all.txt读取IP地址，在email.yaml中找到对应IP的上一行邮箱并输出对应关系，但因re.search的部分匹配特性（如1.1.1.1会匹配到1.1.1.12），导致邮箱匹配错误，仅输出一条错误结果，需修正以得到三个正确的对应关系。

现有代码 #

import re
import smtplib
import ssl
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from email.header import Header
from datetime import datetime

with open('all.txt', 'r') as names_file:
    with open('email.yaml', 'r') as emails_file:
        names = names_file.readlines()
        emails = emails_file.readlines()

        for name in names:
            name = name.strip()
            for i, email in enumerate(emails):
                email = re.sub('-', '', email)
                email = re.sub(' ', '', email)
                if re.search(name, email):
                    prev_email = emails[i-1].strip()
                    prev_email = re.sub('-', '', prev_email)
                    prev_email = re.sub(' ', '', prev_email)
                    html = html.format(name=name)
                    print(f"Name: {name}, Email: {prev_email}")
                    break

文件内容 #

all.txt：

1.1.1.1
1.1.1.12
1.1.1.11

email.yaml：

- emailA@gmail.com
    - 1.1.1.12
    - emailB@gmail.com
    - 1.1.1.1
    - emailC@gmail.com
    - 1.1.1.11

当前输出 #

Name: 1.1.1.1, Email: emailA@gmail.com

期望输出 #

Name: 1.1.1.1, Email: emailB@gmail.com
Name: 1.1.1.12, Email: emailA@gmail.com
Name: 1.1.1.11, Email: emailC@gmail.com

修复方案 #

核心问题是部分匹配导致的误匹配，以下提供两种高效修复方式：

方案1：预构建IP-邮箱映射字典（推荐） #

先遍历email.yaml，将每一组邮箱和对应IP存入字典，后续直接通过IP键查找邮箱，彻底避免正则匹配问题，同时提升查找效率。

修改后代码：

import re

# 预构建IP到邮箱的映射字典
ip_email_map = {}
with open('email.yaml', 'r') as emails_file:
    lines = [line.strip() for line in emails_file.readlines()]
    # 按邮箱+IP的成对结构遍历
    for idx in range(0, len(lines), 2):
        if idx + 1 >= len(lines):
            break
        # 清理邮箱和IP的格式（去除-和空格）
        clean_email = re.sub(r'[- ]', '', lines[idx])
        clean_ip = re.sub(r'[- ]', '', lines[idx+1])
        ip_email_map[clean_ip] = clean_email

# 读取all.txt并输出对应关系
with open('all.txt', 'r') as names_file:
    for ip_line in names_file.readlines():
        target_ip = ip_line.strip()
        if target_ip in ip_email_map:
            print(f"Name: {target_ip}, Email: {ip_email_map[target_ip]}")
        else:
            print(f"Name: {target_ip}, 未找到对应邮箱")

方案2：修改正则为精确匹配 #

若需保留原循环结构，将re.search改为精确匹配，同时转义IP中的.（正则中.为通配符）。

修改后核心循环代码：

import re

with open('all.txt', 'r') as names_file:
    with open('email.yaml', 'r') as emails_file:
        names = names_file.readlines()
        emails = emails_file.readlines()

        for name in names:
            target_ip = name.strip()
            # 转义IP中的.，避免正则通配符干扰
            escaped_ip = re.escape(target_ip)
            for i, line in enumerate(emails):
                clean_line = re.sub(r'[- ]', '', line.strip())
                # 精确匹配整个字符串
                if re.fullmatch(escaped_ip, clean_line):
                    prev_line = emails[i-1].strip()
                    clean_email = re.sub(r'[- ]', '', prev_line)
                    print(f"Name: {target_ip}, Email: {clean_email}")
                    break

验证结果 #

运行任意一种修复方案，均可得到期望的输出结果：

Name: 1.1.1.1, Email: emailB@gmail.com
Name: 1.1.1.12, Email: emailA@gmail.com
Name: 1.1.1.11, Email: emailC@gmail.com

内容的提问来源于stack exchange，提问作者Saeed