pandas 从日期时间对象中提取日期和月份
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Extract day and month from a datetime object
提问by Abhi
I have a column with dates in string format '2017-01-01'. Is there a way to extract day and month from it using pandas?
我有一个字符串格式的日期列'2017-01-01'。有没有办法使用Pandas从中提取日期和月份？
I have converted the column to datetime dtypebut haven't figured out the later part:
我已将列转换为datetime dtype但尚未弄清楚后面的部分：
df['Date'] = pd.to_datetime(df['Date'], format='%Y-%m-%d')
df.dtypes:
Date datetime64[ns]
print(df)
Date
0 2017-05-11
1 2017-05-12
2 2017-05-13
回答by YOBEN_S
With dt.dayand dt.month--- Series.dt
随着dt.day和dt.month---Series.dt
df = pd.DataFrame({'date':pd.date_range(start='2017-01-01',periods=5)})
df.date.dt.month
Out[164]:
0 1
1 1
2 1
3 1
4 1
Name: date, dtype: int64
df.date.dt.day
Out[165]:
0 1
1 2
2 3
3 4
4 5
Name: date, dtype: int64
Also can do with dt.strftime
也可以做 dt.strftime
df.date.dt.strftime('%m')
Out[166]:
0 01
1 01
2 01
3 01
4 01
Name: date, dtype: object
回答by aydow
Use dtto get the datetimeattributes of the column.
使用dt来获取datetime列的属性。
In [60]: df = pd.DataFrame({'date': [datetime.datetime(2018,1,1),datetime.datetime(2018,1,2),datetime.datetime(2018,1,3),]})
In [61]: df
Out[61]:
date
0 2018-01-01
1 2018-01-02
2 2018-01-03
In [63]: df['day'] = df.date.dt.day
In [64]: df['month'] = df.date.dt.month
In [65]: df
Out[65]:
date day month
0 2018-01-01 1 1
1 2018-01-02 2 1
2 2018-01-03 3 1
Timing the methods provided:
定时提供的方法：
Using apply:
使用apply：
In [217]: %timeit(df['date'].apply(lambda d: d.day))
The slowest run took 33.66 times longer than the fastest. This could mean that an intermediate result is being cached.
1000 loops, best of 3: 210 μs per loop
Using dt.date:
使用dt.date：
In [218]: %timeit(df.date.dt.day)
10000 loops, best of 3: 127 μs per loop
Using dt.strftime:
使用dt.strftime：
In [219]: %timeit(df.date.dt.strftime('%d'))
The slowest run took 40.92 times longer than the fastest. This could mean that an intermediate result is being cached.
1000 loops, best of 3: 284 μs per loop
We can see that dt.dayis the fastest
我们可以看到这dt.day是最快的
回答by Babak
A simple form:
一个简单的表格：
df['MM-DD'] = df['date'].dt.strftime('%m-%d')
回答by Peybae
This should do it:
这应该这样做：
df['day'] = df['Date'].apply(lambda r:r.day)
df['month'] = df['Date'].apply(lambda r:r.month)
