title: how can we use Coalesce in python for multiple data frames using pandas
body: <p>How can we use Coalesce with multiple data frames. </p>
  
  <p><code>columns_List = Emp_Id, Emp_Name, Dept_Id...</code></p>
  
  <p>I have two data frames getting used in python script. <code>df1[Columns_List]</code> , <code>df2[columns_List]</code>. In both the dataframes  i have same columns used but i will be having different values in both dataframes. </p>
  
  <p>How can i use Coalesce so that lets say :In Dataframe <code>df1[Columns_List]</code> -- I have <code>Emp_Name null</code> then i want to pick <code>Emp_Name</code> from <code>df2[Columns_list]</code>. </p>
  
  <p>I am trying to create an output CSV file. </p>
  
  <p>Please sorry if my framing of question is wrong..</p>
  
  <p>Please find below sample data. </p>
  
  <p>For Dataframe1 -- df1[Columns_List] .. Please find below output</p>
  
  <pre><code>EmpID,Emp_Name,Dept_id,DeptName
  1,,1,
  2,,2,
  </code></pre>
  
  <p>For Dataframe2 -- df2[Columns_List] .. Please find below output</p>
  
  <pre><code>EmpID,Emp_Name,Dept_id,DeptName
  1,XXXXX,1,Sciece
  2,YYYYY,2,Maths
  </code></pre>
  
  <p>I have source as Json file. Once i parse the data by python , i am using 2 dataframes in the same script. In Data frame 1 ( df1) i have Emp_Name &amp; Dept_Name as null. In that case i want to pick data from Dataframe2 (df2). </p>
  
  <p>In the above example i have provided few columns. But i may have n number of columns. but column ordering and column names will be always same. I am trying to achieve in such a way if any of the column from df1 is null then i want to pick value from df2. </p>
  
  <p>Is that possible.. Please help me with any suggestionn... </p>