Find unique string values in DataFrame that are not integer strings nor floats.

df_unique_values.py

def get_unique_tracker_list(dataframe):
    """This function looks for unique string values in a dataframe."""
    
    mylist = list(pd.Series(dataframe.values.ravel()).unique())
    
    # Convert every element to a string.
    templist = map(str, mylist)
    
    # Return only the strings and deal with the floats. 
    mynewlist = [s for s in templist if s.replace(".", "", 1).isdigit() == False]
    
    return mynewlist