如何使用 Python 仅打印文本文件中字符串的第一个实例？

Question

I am trying to extract data from a .txt file in Python. My goal is to capture the last occurrence of a certain word and show the next line, so I do a reverse () of the text and read from behind. In this case, I search for the word 'MEC', and show the next line, but I capture all occurrences of the word, not the first.

Any idea what I need to do?

Thanks!

This is what my code looks like:

import re

from file_read_backwards import FileReadBackwards

with FileReadBackwards("camdex.txt", encoding="utf-8") as file:
    for l in file:
        lines = l

        while line:
            if re.match('MEC', line):
                x = (file.readline())
                x2 = (x.strip('\n'))
                print(x2)
                break
            line = file.readline()

The txt file contains this:

MEC
29/35
MEC
28,29/35

And with my code print this output:

28,29/35
29/35

And my objetive is print only this:

28,29/35

Answer 1

Get rid of the extra imports and overhead. Read your file normally, remembering the last line that qualifies.

with ("camdex.txt", encoding="utf-8") as file:
    for line in file:
        if line.startswith("MEC"):
            last = line

print(last[4:-1])    # "4" gets rid of "MEC "; "-1" stops just before the line feed.

If the file is very large, then reading backwards makes sense -- seeking to the end and backing up will be faster than reading to the end.

Answer 2

This will give you the result as well. Loop through lines, add the matching lines to an array. Then print the last element.

import re
with open("data\camdex.txt", encoding="utf-8") as file:
    result = []
    for line in file:
        if re.match('MEC', line):
            x = file.readline()
            result.append(x.strip('\n'))

print(result[-1])