title: How to get the inner indexes of a nested dictionary in python
body: <p>I have a dictionary like</p>
  
  <pre><code>A = {1:{1:50,2:60,5:90},2:{7:55,10:102},4:{10:100,12:40}}
  </code></pre>
  
  <p>How can i access the inner indexes of the dictionary i.e the keys 1,2,5  or the keys 10 and 12
  I mean i want access these elements to store them in specific places of an array, but while using a loop, since some keys are absent, there is some kind of an error.(when i tried using A[i][j] in my nested loops).
  How to tackle this unevenness of keyss</p>