Question

我有一个包含超过1000万行的文本文件。这样的行：

37024469;196672001;255.0000000000
37024469;196665001;396.0000000000
37024469;196664001;396.0000000000
37024469;196399002;85.0000000000
37024469;160507001;264.0000000000
37024469;160506001;264.0000000000

如您所见，分隔符是“;”。我想根据第二个元素使用python对这个文本文件进行排序。我不能使用拆分功能。因为它会导致MemoryError。我该怎么办呢？

Answer 1

不要在内存中排序1000万行。将其拆分为：

运行100个100k行排序（使用该文件作为迭代器，结合islice()或类似选择批处理）。写出在其他地方分开文件。

合并已排序的文件。这是一个合并生成器，您可以传递100个打开的文件，它将按排序顺序生成行。逐行写入新文件：

import operator

def mergeiter(*iterables, **kwargs):
    """Given a set of sorted iterables, yield the next value in merged order

    Takes an optional `key` callable to compare values by.
    """
    iterables = [iter(it) for it in iterables]
    iterables = {i: [next(it), i, it] for i, it in enumerate(iterables)}
    if 'key' not in kwargs:
        key = operator.itemgetter(0)
    else:
        key = lambda item, key=kwargs['key']: key(item[0])

    while True:
        value, i, it = min(iterables.values(), key=key)
        yield value
        try:
            iterables[i][0] = next(it)
        except StopIteration:
            del iterables[i]
            if not iterables:
                raise

Answer 2

基于Sorting a million 32-bit integers in 2MB of RAM using Python：

import sys
from functools import partial
from heapq import merge
from tempfile import TemporaryFile

# define sorting criteria
def second_column(line, default=float("inf")):
    try:
        return int(line.split(";", 2)[1]) # use int() for numeric sort
    except (IndexError, ValueError):
        return default # a key for non-integer or non-existent 2nd column

# sort lines in small batches, write intermediate results to temporary files
sorted_files = []
nbytes = 1 << 20 # load around nbytes bytes at a time
for lines in iter(partial(sys.stdin.readlines, nbytes), []):
    lines.sort(key=second_column) # sort current batch
    f = TemporaryFile("w+")
    f.writelines(lines)
    f.seek(0) # rewind
    sorted_files.append(f)

# merge & write the result
sys.stdout.writelines(merge(*sorted_files, key=second_column))

# clean up
for f in sorted_files:
    f.close() # temporary file is deleted when it closes

heapq.merge() has key parameter since Python 3.5。您可以尝试使用mergeiter() from Martijn Pieters' answer或在较旧的Python版本上执行Schwartzian transform：

iters = [((second_column(line), line) for line in file)
         for file in sorted_files] # note: this makes the sort unstable
sorted_lines = (line for _, line in merge(*iters))
sys.stdout.writelines(sorted_lines)

用法：

$ python sort-k2-n.py < input.txt > output.txt

Answer 3

您可以通过os.system()调用bash函数sort

来执行此操作

sort -k2 yourFile.txt

使用Python对文本文件进行排序

3 个答案: