将元素追加到二进制文件 [英] Append element to binary file

问题描述

我的目标是:打开一个 binary 文件，将每100个值存储(附加)到该文件中，然后继续进行直到完成.为此，我使用以下简单循环来模拟这一点:

My goal is: Open a binary file, store (append) every 100 values into this file, and continue doing so until finishing. To do so, I use the following simple loop to simulate that:

import numpy as np
import random

alist=[]
c = 1

for i in range(1000):
    alist.append(i)
    if i == (c*100):
        np.array(alist).tofile("file.bin")
        print alist
        c = c + 1
        alist[:] = [] # clear the list before continuing

但是，当我检查file.bin的大小时，我感到numpy没有追加，而是要替换而不是我想要的.该如何解决?

However, when I check the size of file.bin, I feel numpy does not append rather it is replacing which is not what I want. How to fix that?

谢谢.

推荐答案

当然，每次(重新)打开要写入的文件时，numpy都会替换/覆盖旧数据.这几乎是大多数tofile()类似函数的通用行为(不仅在numpy中).

Of course numpy is replacing/overwriting your old data every time you (re-)open the file for writing. This is almost universal behavior of most tofile() like functions (and not only in numpy).

解决方案:在循环之前打开要写入的文件句柄，然后将其传递给tofile()函数.像这样:

Solution: Open a file handle for writing before the loop and pass that to tofile() function. Like this:

import numpy as np
import random

alist=[]
c = 1
with open("file.bin", "wb") as f: # or choose 'w+' mode - read "open()" documentation
    for i in range(1000):
        alist.append(i)
        if i == (c*100):
            np.array(alist).tofile(f)
            print alist
            c = c + 1
            alist[:] = [] # clear the list before continuing

现在，代码在进入循环之前打开文件，并且tofile()方法重新使用已经打开的文件句柄，而不是重新打开，从而覆盖了现有文件(在循环运行中创建).

Now the code opens the file before entering the loop and tofile() method re-uses an already opened file handle instead of re-opening and thus overwriting an existing file (created in the run of the loop).

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