Bring columns to front of dataframe
cols = list(df1)
cols.insert(0, cols.pop(cols.index('return_datetime'))) #3rd
cols.insert(0, cols.pop(cols.index('order_datetime'))) #2nd
cols.insert(0, cols.pop(cols.index('package_req_id'))) #1st
df1 = df1.ix[:, cols]