如何从Python中的特定文本行中提取文本？

Question

如何使用Python从文本文件内的特定文本行中提取文本？

Answer 1

If you want to read the 10th line:

with open("file.txt") as f:
    for i in range(9):
        f.next()
    print f.readline()

This doesn't read the whole file in memory.

Answer 2

The following Python example should extract the correct line number, but it is horribly inefficient:

f = open('file.txt')
print f.readlines()[line_number]

Answer 3

The simplest method:

print list( open('filename') )[line_number]

That's gonna read in the whole file which may not be a good idea. A more efficient technique would depend on how you are using it.