title: Pandas: Dealing with missing column in input dataframe
body: <p>I have a python code which performs mathematical calculations on multiple columns of the dataframe. This input comes from various sources so there is a possibility that sometimes one column is missing from the same.</p>
  
  <p>This column is missing because its insignificant but i need to have a null column atleast for the code to run without errors.</p>
  
  <p>I can add a null column using if loop but there are around 120 columns and i do not want to slow down the code. Is there any other way where the code can check each column is present in the original dataframe and then if any column is not present it adds a null column and then starts with execution of the actual code?</p>