当行以字符串开头时，如何按整数对文本文件进行排序？

import re

def sort_text_file(filename, startswith_str):
    lines_with_startswith = []
    with open(filename, 'r') as file:
        for line in file:
            if line.startswith(startswith_str):
                lines_with_startswith.append(line)
    
    numbers = []
    for line in lines_with_startswith:
        integers = re.findall(r'\d+', line)
        if integers:
            numbers.append(int(integers[0]))
    
    sorted_numbers = sorted(numbers)
    
    sorted_lines = []
    for number in sorted_numbers:
        for line in lines_with_startswith:
            if str(number) in line:
                sorted_lines.append(line)
                break
    
    with open('sorted_' + filename, 'w') as file:
        file.writelines(sorted_lines)

# 示例使用
sort_text_file('input.txt', 'prefix_')