Python - 一次从文件中读取 1000 行 [英] Python - read 1000 lines from a file at a time

问题描述

我检查了 this, this 和 这个.

I've checked this, this and this.

第三个链接似乎有答案，但它没有完成工作.

The 3rd link seemed to have the answer yet it didn't do the job.

我无法找到将整个文件放入主内存的解决方案，因为我将处理的文件非常大.所以我决定使用 islice 如第三个链接所示.前 2 个链接无关紧要，因为它们仅用于 2 行或读取 1000 个字符.而我需要 1000 行. 现在 N 是 1000

I can't have a solution where the whole file is brought to main memory, as the files I'll be working with will be very large. So I decided to use islice as shown in the 3rd link. First 2 links were irrelevant as they used it for only 2 lines or read 1000 characters. Whereas I need 1000 lines. for now N is 1000

我的文件包含一百万行:

示例:

1 1 1
1 2 1
1 3 1
1 4 1
1 5 1
1 6 1
1 7 1
1 8 1
1 9 1
1 10 1

所以如果我一次读取 1000 行，我应该遍历 while 1000 次，但是当我打印 p 来检查我经历了多少次，它并没有停在 1000 处.在运行我的程序 1400 秒后，它达到了 19038838！！

So if I read 1000 lines at a time, I should go through the while 1000 times, yet when I print p to check how many times I've been in through, it doesn't stop at a 1000. It reached 19038838 after running my program for 1400 seconds!!

代码:

def _parse(pathToFile, N, alg):
    p = 1
    with open(pathToFile) as f:
        while True:
            myList = []
            next_N_lines = islice(f, N)
            if not next_N_lines:
                break
            for line in next_N_lines:
                s = line.split()
                x, y, w = [int(v) for v in s]
                obj = CoresetPoint(x, y)
                Wobj = CoresetWeightedPoint(obj, w)
                myList.append(Wobj)
            a = CoresetPoints(myList)
            client.compressPoints(a) // This line is not the problem
            print(p)
            p = p+1
    c = client.getTotalCoreset()
    return c

我做错了什么?

推荐答案

正如@Ev.kounis 所说，您的 while 循环似乎无法正常工作.

As @Ev.kounis said your while loop doesn't seem to work properly.

我建议在这样的时间为大量数据使用 yield 函数:

I would recommend to go for the yield function for chunk of data at a time like this:

def get_line():
    with open('your file') as file:
        for i in file:
            yield i

lines_required = 1000
gen = get_line()
chunk = [next(gen) for i in range(lines_required)]

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