python - 如何使用 Python 读取 Fortran 创建的整个二进制文件

Question

我使用 Fortran 创建一个包含多行的二进制文件:

Program write_binary
implicit none
integer i
real x
open(10,file="test.dat",form="unformatted")
do i=1,10
   write(10),i*1.0,i*2.0
end do
close(10)
end

然后我使用 Python，尝试读取整个文件。但是，FortranFile 包只能逐行读取(参见下面的代码)。有什么方法可以读取 Fortran 创建的二进制文件的所有行？非常感谢。

from scipy.io import FortranFile
import numpy as np
f=FortranFile('test.dat','r')
x=read_reals(dtype='f4')
print(x)

Answer 1

我经常用 Fortran 编写数据并用 Python 读取数据。我将在这里针对多个 3D 阵列的情况进行解释，因为它更通用并且更容易适应 1D 阵列。

在 Fortran 中，我使用以下循环写入数据:

file = 'my_fortran_data.dat'
open(99, file=file, status = 'replace', action = 'write', form = 'unformatted', access='stream')
    do k = 1,L
        do j = 1,M
            do i = 1,N
                write(99) u(i,j,k), v(i,j,k), w(i,j,k)
            end do
        end do
    end do
close(99)

请注意，我在 stream 访问中写入数据。因此我不记录每条记录的开始和结束(使文件大小更小)。

在 Python 中，我使用以下函数读取数据:

def read_data(file, dtype, stream):
    """
    Return the components of a 3D vector field stored in binary format.
    The data field is supposed to have been written as: (for k; for j; for i;) where the last dimension
    is the quickest varying index. Each record should have been written as: u, v, w.
    The returned components are always converted in np.double precision type.

    Args:
        dim: number of dimensions
        dtype: numpy dtype object. Single or double precision expected.
        stream: type of access of the binary output. If true, the file can only contain data. 
    If false, there is a 4-byte header and footer around each "record"
            in the binary file (can happen in some Fortran compilers if access != 'stream').
    """
    if stream:
        shape = (L, M, N, 3)
        f = open(file, 'rb')
        data = np.fromfile(file=f, dtype=dtype).reshape(shape)
        f.close()
        u = data[:, :, :, 0].transpose(2, 1, 0)
        v = data[:, :, :, 1].transpose(2, 1, 0)
        w = data[:, :, :, 2].transpose(2, 1, 0)
        del data

    else:
        shape = (L, M, N, 5)
        f = open(file, 'rb')
        data = np.fromfile(file=f, dtype=dtype).reshape(shape)
        f.close()
        u = data[:, :, :, 1].transpose(2, 1, 0)
        v = data[:, :, :, 2].transpose(2, 1, 0)
        w = data[:, :, :, 3].transpose(2, 1, 0)
        del data

    u = u.astype(np.float64, copy=False)
    v = v.astype(np.float64, copy=False)
    w = w.astype(np.float64, copy=False)
    return(u, v, w)

请注意，我总是将数据转换为 double ，但如果不需要，您可以省略这最后一步。

对于您的情况，使用 shape=(10,2) 进行 stream 访问，否则使用 shape=(10,4)。