Coursera《Python数据科学导论》作业1正则表达式问题求助

Let's break down what's wrong with your current regex pattern and fix it to correctly extract the required fields from your log data.

What's Wrong with Your Original Pattern #

Your regex has several key issues that prevent it from matching the log lines:

1. Host Group: You're trying to capture the IP address but your named host group uses \w* (which matches word characters, not IPs) while the actual IP pattern is outside the group. This means the host group captures nothing.
2. User Name Group: Your pattern doesn't account for the - case (when no username is present), and the named group is set to \w* (capturing empty) instead of the actual username value.
3. Time Group: The time string is inside square brackets, but your time group captures \w* (nothing) while the actual time is in an unnamed sub-group.
4. Request Group: Similar to time, the request is inside quotes but your request group captures nothing, leaving the actual request in an unnamed group.

Corrected Code with Working Regex #

Here's the fixed version of your function, with a regex that properly matches all parts of the log lines:

import re

def logs():
    with open("assets/logdata.txt", "r") as file:
        logdata = file.read()
    
    # Corrected regex pattern with named groups
    pattern = r"""
    ^(?P<host>\d+\.\d+\.\d+\.\d+)  # Capture the IP address as 'host'
    \s-\s                         # Match the "-" separator between host and user
    (?P<user_name>-|\w+)          # Capture username (either "-" or alphanumeric)
    \s\[                          # Match the opening bracket for time
    (?P<time>[^\]]+)              # Capture everything inside the brackets as 'time'
    \]\s"                         # Match closing bracket and opening quote
    (?P<request>[^"]+)            # Capture everything inside quotes as 'request'
    "
    """
    
    # Use MULTILINE to match each line, VERBOSE for readability
    matches = re.finditer(pattern, logdata, re.VERBOSE | re.MULTILINE)
    
    result = []
    for item in matches:
        parsed_dict = item.groupdict()
        print(parsed_dict)
        result.append(parsed_dict)
    
    return result

# Run the function to test
logs()

Key Improvements #

• Host: Directly matches IP addresses with \d+\.\d+\.\d+\.\d+ and captures it in the host group.
• User Name: Handles both cases (- or a username) with (?P<user_name>-|\w+).
• Time: Captures the full time string inside brackets using [^\]]+ (matches everything until the closing ]).
• Request: Captures the full request inside quotes using [^"]+ (matches everything until the closing ").
• Multiline Support: Added re.MULTILINE so ^ matches the start of each line in the log file.

Sample Output #

For your test log lines, this will produce:

{"host":"159.253.153.40", "user_name":"-", "time":"21/Jun/2019:15:46:10 -0700", "request":"POST /e-business HTTP/1.0"}
{"host":"136.195.158.6", "user_name":"feeney9464", "time":"21/Jun/2019:15:46:11 -0700", "request":"HEAD /open-source/markets HTTP/2.0"}

内容的提问来源于stack exchange，提问作者BryantHsiung