title: Get the unique values of column in dataframe on the other column condition in python
body: <p>Dataframe: </p>
  
  <pre><code>id  name        count
  123 ssdf        1
  123 wasdfasdf   1
  234 ewdd        0
  345 efdfg       2
  345 efg         1
  345 gfdfg       1
  456 gfdfg       1
  456 ffg         1
  567 vd          3
  </code></pre>
  
  <p>Here there is id and count columns, how many id's are there where count is 1. 
  If one id has 1,1,1 then i need that id in the result list. 
  if the id has 0,1,1 then never mind. 
  if the id has 0,3,0 then never mind. </p>
  
  <p>Expected result:</p>
  
  <pre><code>list_1 = ['123','456']
  </code></pre>
  
  <p>also can i please expect the answer as the function in python.</p>