如何在python中使Fortran的'access = stream'等效

Question

Let's say i'm making a loop, and after each iteration, y want to extend some array.

iter 1 ------------> iter 2 --------------> iter 3-------------->....

shape=[2,4]---->shape=[2,12]----->shape=[2,36]---->....

in fortran i used to do this by appending the new numbers to a binary file with:

OPEN(2,file='array.in',form='unformatted',status='unknown',access='stream')
write(2) newarray

so this would extend the old array with new values at the end.

i wish to do the same in python. This is my attempt so far:

import numpy as np

#write 2x2 array to binfile
bintest=open('binfile.in','wb')
np.ndarray.tofile(np.array([[1.0,2.0],[3.0,4.0]]),'binfile.in')
bintest.close()

#read array from binfile 
artest=np.fromfile('binfile.in',dtype=np.float64).reshape(2,2)

But i can't get it to extend the array. Lets say.. by appeding another [[5.0,5.0],[5.0,5.0]] at the end,

#append new values.
np.ndarray.tofile(np.array([[5.0,5.0],[5.0,5.0]]),'binfile.in')

to make it [[1.0,2.0,5.0,5.0],[3.0,4.0,5.0,5.0]] after the reading. How can i do this?

The other problem i have, is that i would like to be able to make this without knowing the shape of the final array (i know it would be 2 xn ). But this is not so important.

edit: the use of 'access=stream' is only to skip having to read format headers and tails.

Answer 1

This does the trick:

import numpy as np

#write
bintest=open('binfile.in','ab')
a=np.array([[1.0,2.0],[3.0,2.0]])
a.tofile(bintest)
bintest.close()

#read
array=np.fromfile('binfile.in',dtype=np.float64)

this way, each time its run, it appends the new array to the end of the file.