在数据框

Question

我期待按日期过滤以下df，期待在索引值中仅按星期三过滤：

begin=2015-05-14
end=2015-05-22

Date
2015-05-14   81.370003  6.11282  39.753  44.950001
2015-05-15   80.419998  6.03380  39.289  44.750000
2015-05-18   80.879997  6.00746  41.249  44.360001
2015-05-19   80.629997  6.10465  41.047  40.980000
2015-05-20   80.550003  6.14370  41.636  42.790001
2015-05-21   80.480003  6.16096  42.137  43.680000
2015-05-22   80.540001  6.13916  42.179  43.490002

继续......

这就是我的尝试：

df1=df[df.index.dayofweek == 2]

然后尝试：

df.index = pd.date_range(begin,end,freq='W')

在两种情况下均未成功

所需的输出是相同的df，仅返回星期三的行。

Answer 1

你可以先看过滤：

df = df.loc[begin:end]
df1=df[df.index.dayofweek == 2]
print (df1)
                    a       b       c          d
2015-05-20  80.550003  6.1437  41.636  42.790001

Answer 2

不是最优雅的解决方案，可能远离pythonic。但它会做到这一点。 （在运行之前将所有数据放在pandas数据帧中）

import datetime
import pandas as pd
import time
import calendar
b=0
for date in a:
    x = time.strptime(date, "%Y-%m-%d") #strips date in to its components
    year=x.tm_year #get year this is necessary for the way datetime.date works (to my best understanding)
    month=x.tm_mon #get month
    day=x.tm_mday #get day
    dayofweek=datetime.date(year,month,day).weekday() #use above to determine day of the week
    if dayofweek is 2:    
        df.set_value(b, 'col6', True) #create extra column that is True if day of week is Wednesday
    b=b+1
df=df.loc[df['col6'] == True] #drop everything in df that is not a Wednesday observation