title: python difference between the two form of matrix x[i,j] and x[i][j]
body: <p>i want to understand the difference between <code>x[i,j]</code> and <code>x[i][j]</code> where x is a matrix </p>
  
  <pre><code>x = np.zeros((N,M))
  </code></pre>
  
  <p>The answer that i found while doing the research is always about array with 2D dimension but in my case i have a matrix with two index to work with i and j and i need to manipulate the matrix according the index with a for loop.</p>
  
  <pre><code>    for i in range(1,N+1):
          for j in range(1,M+1):
              x[i-1][j-1]=random.uniform(5,10)
  </code></pre>
  
  <p>so can you help me understand the difference between <code>x[i,j]</code> and <code>x[i][j]</code>and to be more clear for each i(base station) there is a number of j (users)</p>