从C中创建的二进制文件中读取双精度的最佳方法是什么？ [英] What is the best method to read a double from a Binary file created in C?

问题描述

C程序将连续的double吐出到二进制文件中。我希望将它们读入Python。我尝试使用 struct.unpack（'d'，f.read（8））

A C program spits out consecutive doubles into a binary file. I wish to read them into Python. I tried using struct.unpack('d',f.read(8))

编辑：
我在C语言中使用以下命令编写了一个随机双精度数

I used the following in C to write a random double number

r = drand48();
fwrite((void*)&r, sizeof(double), 1, data);

错误现已修复，但我无法读取第一个值。对于所有的0.000 ..数字，它读为3.90798504668055，但是其余的都很好。

The Errors are now fixed but I cannot read the first value. for an all 0.000.. number it reads it as 3.90798504668055 but the rest are fine.

推荐答案

我认为您实际上正在阅读编号正确，但显示感到困惑。当我从您提供的文件中读取数字时，我得到 3.907985046680551e-14 -这几乎但不是零（展开形式为0.000000000000039）。我怀疑您的C代码只是以比python更低的精度打印它。

I think you are actually reading the number correctly, but are getting confused by the display. When I read the number from your provided file, I get "3.907985046680551e-14" - this is almost but not quite zero (0.000000000000039 in expanded form). I suspect your C code is just printing it with less precision than python is.

我刚刚尝试用C读取文件，但我得到了相同的结果结果（尽管精度稍差：3.90799e-14）（使用printf（％g，val）），所以我认为如果该值不正确，则发生在书写侧，而不是读取侧。

I've just tried reading the file in C, and I get the same result (though slightly less precision: 3.90799e-14) (using printf("%g", val)), so I think if this value is incorrect, it's happened on the writing side, rather than the reading.

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