不要使用阅读线!

我的解决方案是:

with open(filename) as f:
    specify = [26, 30]
    results = list(
        map(lambda line: line[1],
            filter(lambda line: line[0] in specify,
                   enumerate(f))
            )
    )

对6.5G文件进行如下测试:

import time

filename = 'a.txt'
start = time.time()
with open(filename, 'w') as f:
    for i in range(10_000_000):
        f.write(f'{str(i)*100}\n')       
end1 = time.time()

with open(filename) as f:
    specify = [26, 30]
    results = list(
        map(lambda line: line[1],
            filter(lambda line: line[0] in specify,
                   enumerate(f))
            )
    )
end2 = time.time()
print(f'write time: {end1-start}')
print(f'read time: {end2-end1}')
# write time: 14.38945460319519
# read time: 8.380386352539062

对于阿洛克·辛格尔的回答，这是一个更好的小变化

fp = open("file")
for i, line in enumerate(fp,1):
    if i == 26:
        # 26th line
    elif i == 30:
        # 30th line
    elif i > 30:
        break
fp.close()

@OP，你可以使用枚举

for n,line in enumerate(open("file")):
    if n+1 in [26,30]: # or n in [25,29] 
       print line.rstrip()

从某一行读出:

n = 4   # for reading from 5th line
with open("write.txt",'r') as t:
     for i,line in enumerate(t):
         if i >= n:             # i == n-1 for nth line
            print(line)

这个怎么样:

>>> with open('a', 'r') as fin: lines = fin.readlines()
>>> for i, line in enumerate(lines):
      if i > 30: break
      if i == 26: dox()
      if i == 30: doy()

file = '/path/to/file_to_be_read.txt'
with open(file) as f:
    print f.readlines()[26]
    print f.readlines()[30]

使用with语句打开文件，打印第26行和第30行，然后关闭文件。简单!