Python 2.7: How to save two arrays with different lengths to file?

Question

I'm trying to save two arrays (arr1, arr2) to a file horizontally. The problem is the two arrays have different lengths. So I can't use np.v_stack() to concatenate them. The two arrays I want to save: arr1 (5, 3):

array([[-15.220009 ,  10.6649946,  -0.8999929],
       [-15.000009 ,  11.3639946,  -1.5949929],
       [-14.036009 ,   9.9939946,  -0.3249929],
       [-12.958009 ,  10.9589946,   0.2050071],
       [-12.179009 ,  10.3039946,   0.5970071]])

arr2 (4, 3):

array([[-15.809009 ,  10.0499946,  -1.4429929],
       [-15.804009 ,  10.9649946,  -0.1329929],
       [-13.677009 ,   9.3459946,  -1.1249929],
       [-13.420009 ,  11.4869946,   1.0390071]])

The output I'm expecting:

-15.220009,  10.6649946,  -0.8999929, -15.809009,  10.0499946,  -1.4429929
-15.000009,  11.3639946,  -1.5949929, -15.804009,  10.9649946,  -0.1329929
-14.036009,   9.9939946,  -0.3249929, -13.677009,   9.3459946,  -1.1249929
-12.958009,  10.9589946,   0.2050071, -13.420009,  11.4869946,   1.0390071
-12.179009,  10.3039946,   0.5970071

I have searched on google but can't find a useful solution.

Answer 1

arr = [[-15.220009, 10.6649946, -0.8999929],
   [-15.000009, 11.3639946, -1.5949929],
   [-14.036009, 9.9939946, -0.3249929],
   [-12.958009, 10.9589946, 0.2050071],
   [-12.179009, 10.3039946, 0.5970071]]

arr2 = [[-15.809009, 10.0499946, -1.4429929],
   [-15.804009, 10.9649946, -0.1329929],
   [-13.677009,  9.3459946, -1.1249929],
   [-13.420009, 11.4869946, 1.0390071]]

for i in range(max(len(arr), len(arr2))):
    str1 = (", ".join(map(str, arr[i]))) if i < len(arr) else ""
    str2 = (", ".join(map(str, arr2[i]))) if i < len(arr2) else ""
    print str1 + ', ' + str2

This doesn't save it to a file, but you could replace the print with saving to a file. Note that if the first array is shorter than the second, the second one's extra rows will appear below the first array.

Edit

One Line solution

print "\n".join([", ".join(map(str, (arr[i] if i < len(arr) else []) + (arr2[i] if i < len(arr2) else []))) for i in range(max(len(arr), len(arr2)))])

Answer 2

I have got the expected output with several steps. First, I use np.hstack() to concatenate the slice of the larger with the smaller. Then open a file and write the arr3 and arr1[-1:] (the leftover portion of the larger) to a file in order using np.savetxt(). For example:

arr3=np.hstack((arr1[:-1], arr2))
with open('out.dat', 'w') as output:
    np.savetxt(output, arr3, fmt=','.join(['% 12.7f']*6))
    np.savetxt(output, arr1[-1:], fmt=','.join(['% 12.7f']*3))

Answer 3

 x = np.concatenate((arr,arr2))
 np.save('fileName', x)