如何从 python 中的 txt 文件中选择要打印的行

Question

I want to print a specific line from a txt file like from a txt file like this:

"line number 1"

"line number 2"

"line number 3"

I want to print line number 3 and 2 how do I do that?

Answer 1

Let's say you want to print from start_line to end_line . You can do as follows:

with open("test.txt", "r") as f:
    rows = f.readlines()[start_line - 1 : end_line]
    print(rows)

If start_line is 2 and end_line is 3 , it will print 2nd and 3rd lines of test.txt

Answer 2

This code will help you:

from collections import deque

try:
    num = int(input("Number of last lines to print:"))
except:
    num = 1

a_file = open("data.txt")

lines = a_file.readlines()

for line in deque(lines, num):
    print(line)

Answer 3

To avoid loading the whole file in memory do not use readlines :

fname = "data.txt"
skip_num = 2
with open(fname) as f:
    for _ in range(skip_num):
        f.readline()
    for line in f:
        print(line)

Cheers!