文件访问前进

Question

我需要逐行读取一个文件,我需要查看"下一行",所以首先我将文件读入列表,然后循环浏览列表...不知怎的,这似乎很粗鲁,建立列表可能是变得昂贵.

for line in open(filename, 'r'):
    lines.append(line[:-1])

for cn in range(0, len(lines)):
    line = lines[cn]
    nextline = lines[cn+1] # actual code checks for this eof overflow

必须有更好的方法来迭代线,但我不知道如何向前看

Answer 1

您可能正在寻找类似itertools 的成对配方.

from itertools import tee, izip
def pairwise(iterable):
    "s -> (s0,s1), (s1,s2), (s2, s3), ..."
    a, b = tee(iterable)
    next(b, None)
    return izip(a, b)

with open(filename) as f: # Remember to use a with block so the file is safely closed after
    for line, next_line in pairwise(f):
        # do stuff