def post_hdfc(r):
    if (r['balance_dt']>= pd.to_datetime('2017-06-01')) & (r['balance_dt']<= pd.to_datetime('2017-06-30')):
        return r['balance_am_01'].sum()
    if (r['balance_dt']>= pd.to_datetime('2017-07-01')) & (r['balance_dt']<= pd.to_datetime('2017-07-31')):
        return r[['balance_am_01','balance_am_02']].sum()
df_hdfctoobc['hdfc_post_spend'] = df_hdfctoobc.apply(post_hdfc,axis=1)

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