根据第二个过滤数据帧的结果过滤条件数据帧：寻求效率提升

Question

为我笨重的坏人寻求更有效的解决方案

我有一个非常大的数据框，其中包含许多符号的所有详细股票数据。看起来像这样df:

        symbol        time   open   high    low  close  volume
0         AEHR  1628656380    652    652    652    652     200
1         AEHR  1628660580    646    646    646    646     100
2         AEHR  1628668380    634    634    634    634     300
3         AEHR  1628668920    606    608    606    608     402
4         AEHR  1628669100    615    615    615    615     100
...        ...         ...    ...    ...    ...    ...     ...
4266849   UPST  1631303160  26753  26753  26753  26753     163
4266850   UPST  1631303340  26805  26805  26805  26805     231
4266851   UPST  1631303520  26768  26768  26768  26768     226
4266852   UPST  1631303760  26819  26819  26819  26819    1964
4266853   UPST  1631303940  26899  26899  26899  26899     157

我想切片以进行有效的进一步处理。我只想保留与此“交易”数据库db_buy 列表相关的数据：

  Symbol                Time
0    AMD 2019-12-12 09:36:00
1    AMD 2020-01-16 09:33:00
2   BITF 2021-08-03 09:47:00
3   DOCN 2021-06-14 09:32:00
4   NVDA 2020-07-29 09:38:00
5   NVDA 2020-09-25 10:34:00
6   UPST 2021-02-09 09:32:00
7   UPST 2021-03-18 09:32:00

我只想将数据保存在哪里

• df['symbol'] = df_buy['Symbol'];并且，
• df['time'] > df_buy['Time'] - BDay(25)

---

我的解决方案感觉几行就可以完成：

    db_buy.sort_index(inplace=True)
    no_match = np.nan

    # Find start date required for slice
    tickers = pd.DataFrame()
    tickers['Symbol'] = db_buy['Symbol'].unique()
    tickers.sort_index(inplace=True)
    print(tickers)
    for i, row in tickers.iterrows():
        cond = (db_buy['Symbol'] == tickers['Symbol'])
        same_symbol = db_buy[cond]  # gets df of same tickers ['Symbol', 'Time']
        min_date = same_symbol['Time'].min()  # returns min value
        match = no_match if not cond.any() else min_date
        # ^ Returns 'NAN' if cond=false, else match=first row of df which is true
        tickers.loc[i, 'Time'] = match

    # Get data for stocks in buy list only. Time data starting 25 days prior to buy date to now
    cond = (
            (df['Symbol'] == tickers['Symbol']) &
            (df['Time'] > tickers['Time'] + BDay(-25))
    )
    df = df[cond]

cond = (db_buy['Symbol'] == tickers['Symbol']) ValueError：只能比较标签相同的系列对象

Answer 1

您可以结合两个条件使用简单的切片：

# ensure datetime type
df['time'] = pd.to_datetime(df['time'], unit='s')
d_buy['Time'] = pd.to_datetime(d_buy['Time'])

# slice data
df[  df['symbol'].isin(d_buy['Symbol'].unique())            # symbol is in Symbol
   & df['time'].gt(d_buy['Time'].min()-pd.Timedelta('25d')) # time > min(Time)-25days
  ]

输出：

        symbol                time   open   high    low  close  volume
4266849   UPST 2021-09-10 19:46:00  26753  26753  26753  26753     163
4266850   UPST 2021-09-10 19:49:00  26805  26805  26805  26805     231
4266851   UPST 2021-09-10 19:52:00  26768  26768  26768  26768     226
4266852   UPST 2021-09-10 19:56:00  26819  26819  26819  26819    1964
4266853   UPST 2021-09-10 19:59:00  26899  26899  26899  26899     157