def column_dtype_dict(df):
    """Return a dictionary mapping column names to dtypes. 
    Can be used to read in data to inital dataframe with optimized dtypes"""
    dtypes = df.dtypes
    # Pull the column name
    dtypes_col = dtypes.index
    # And the dtype
    dtypes_type = [i.name for i in dtypes.values]
    # Create Dictionary
    column_types = dict(zip(dtypes_col, dtypes_type))
    return column_types