import pandas as pd


class DateFrameHolder:

    def __init__(self, df=None):
        self.df = df or pd.DataFrame()
#        self.df = pd.DataFrame.from_records([dict(a=1, b=2, c=3)] * 4) #TODO: remove

    def append(self, data):
        data = pd.DataFrame.from_records([data])
        self.df = pd.concat([self.df, data], ignore_index=True)

    def clear(self):
        self.df = pd.DataFrame()



from io import BytesIO


def to_excel_binary(df, **kwargs):
    with BytesIO() as out:
        df.to_excel(out, **kwargs)
        res = out.getvalue()
    return res

def to_hdf_binary(df, key="df", **kwargs):
    with BytesIO() as out:
        df.to_hdf(out, key, **kwargs)
        res = out.getvalue()
    return res