Python正则匹配行首单词：提取首个状态为[up]的接口

Got it, let's tackle your two Python regex tasks with clear examples and explanations:

To grab the first word (a sequence of non-whitespace characters) at the start of a line, we can use a regex that targets the beginning of the line and captures the first continuous non-blank segment.

Here's how to implement it:

import re

# For a single line
single_line = "Ethernet1/48       up       up"
first_word_match = re.search(r"^(\S+)", single_line)
if first_word_match:
    print(first_word_match.group(1))  # Output: Ethernet1/48

# For multi-line text
multi_line_text = """
GigabitEthernet0/1   down     down
Ethernet1/48         up       up
Ethernet1/1          up       down
"""
# Iterate through each line and extract the first word
for line in multi_line_text.strip().split("\n"):
    match = re.search(r"^(\S+)", line)
    if match:
        print(match.group(1))

How it works: #

• ^ anchors the match to the start of the line
• (\S+) captures one or more non-whitespace characters (this is our first word)
• re.search() finds the first occurrence of the pattern in the string

Assuming your input is a multi-line string where each line starts with an interface name followed by status values, we can adjust the regex to target lines where the status is up (or [up] if that's your actual format) and capture the first matching interface.

Example Implementation: #

import re

# Sample input content
input_data = """
GigabitEthernet0/1   down     down
Ethernet1/48         up       up
Ethernet1/1          up       down
"""

# Match the first interface where the first status is "up"
# If your status uses brackets (like [up]), replace "up" with "\[up\]" in the regex
interface_match = re.search(r"^(\S+)\s+up", input_data, re.MULTILINE)
if interface_match:
    target_interface = interface_match.group(1)
    print(target_interface)  # Output: Ethernet1/48

Notes: #

• re.MULTILINE makes ^ match the start of every line in the multi-line string, not just the start of the entire string
• If the up status is in a different column (e.g., the second status column), adjust the regex to skip the first status field: r"^(\S+)\s+\S+\s+up"
• For bracketed statuses like [up], escape the brackets: r"^(\S+)\s+\[up\]"

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