Changes a column name in a DataFrame
    Parameters:
    df - DataFrame
        DataFrame to operate on
    col_name - string
        Name of column to change
    new_col_name - string
        New name of column

def col_rename(df,col_name,new_col_name):
    """ Changes a column name in a DataFrame
    Parameters:
    df - DataFrame
        DataFrame to operate on
    col_name - string
        Name of column to change
    new_col_name - string
        New name of column
    """
    col_list = list(df.columns)
    for index,value in enumerate(col_list):
        if value == col_name:
            col_list[index] = new_col_name
            break
    df.columns = col_list