title: how to append every row of pandas dataframe to every row of another dataframe
body: <p>for example, df1 is a 3*2 dataframe, and df2 is a 10*3 dataframe, what I want is to generate a new dataframe of 30*5, where each row in df1 is appended with the 3 columns of df2 for all 10 rows in df2.</p>
  
  <p>I know I can use iteration to append columns of df2 to each row of df1, but I am wondering whether there are some more efficient way to do this in pandas, like its concat functions.</p>
  
  <p>could anyone help?</p>
  
  <p>regards,
  nan</p>