title: Merge multiple list of dict with same value in common key
body: <p>I have 4 list of dicts</p>
  
  <pre><code>list1 = [{'a':0,'b':23}, {'a':3,'b':77},{'a':1,'b':99}]
  
  list2 = [{'a':1,'c':666},{'a':4,'c':546}]
  
  list3 = [{'d':33,'a':3},{'d':1111,'a':4},{'d':76,'a':1},{'d':775,'a':0}]
  
  list4 = [{'a':2,'e':12},{'a':4,'e':76}]
  </code></pre>
  
  <p>Every dict in the list has a common key 'a'. My requirement is 'a' key with same value in dict from all the list should be merged and if a particular key does not exist in the dicts while merging, then assign 0 for those keys or just omit those keys.
  for eg. for key 'a' with value 1, from above example we have 2 dicts, one from list1 i.e {'a':0,'b':23} and one is list3, last dict i.e {'d':775,'a':0}, so 1st we have identified the dicts with same 'a' value, now need to merge these dicts
  i.e {'a':0, 'b':23, 'c':0, 'd':775, 'e':0}, since both the dict didn't have 'c', 'c' is assigned as 0 here</p>
  
  <p>I should get the output as:</p>
  
  <pre><code>[{'a':0,'b':23,'c':0,'d':775, 'e':0},{'a':1,'b':99,'c':666,'d':76,'e':0},{'a':2,'b':0,'c':0,'d':0,'e':12},{'a':3,'b':77,'c':0,'d':33,'e':0}, {'a':4,'b':0,'c':546,'d':1111,'e':76}]
  </code></pre>
  
  <p>usings minimum loops or list comprehension</p>