title: how to append numpy array of different dimension to already existing text file in python
body: <p>I have a code which requires 2xN dimensional matrix written to a text file for every iteration. But the problem is N keeps changing from one iteration to other.</p>
  
  <p>I want to write this data to text file in python, and keep appending newly generated matrix to the old file. But it seems i have to convert numpy array to string before i can append to text file and its hugely time consuming as array to string function for large matrices is really slow.</p>
  
  <p>Hence can somebody please tell me how do i append numpy arrays directly into the text file without converting them to string or list/</p>
  
  <p>Thanks</p>