如何按字母顺序连接Python中的多个排序文件？

Question

如何逐行读取多个CSV输入文件，比较每行中的字符，将先按字母顺序出现的行写入输出文件，然后将最小值文件的指针向前推进，继续与所有文件进行比较，直到达到所有输入文件的末尾为止。下面是一些解决方案的粗略计划。

buffer = []

for inFile in inFiles:

    f = open(inFile, "r")
    line = f.next()
    buffer.append([line, inFile])

#find minimum value in buffer alphabetically...
#write it to an output file...

#how do I advance one line in the file with the min value?
#and then continue the line-by-line comparisons in input files?

Answer 1

您可以使用heapq.merge

import heapq
import contextlib

files = [open(fn) for fn in inFiles]
with contextlib.nested(*files):
    with open('output', 'w') as f:
        f.writelines(heapq.merge(*files))

在Python3.x(3.3+)中：

import heapq
import contextlib

with contextlib.ExitStack() as stack:
    files = [stack.enter_context(open(fn)) for fn in inFiles]
    with open('output', 'w') as f:
        f.writelines(heapq.merge(*files))