使用 python/pandas 将月、日、年转换为月、年？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/40744322/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Convert month,day,year to month,year with python/pandas?
提问by Joan Triay
I have this kind of list of strings with 9000 rows where each row is month/day/year:
我有这种包含 9000 行的字符串列表，其中每一行是月/日/年：
10/30/2009
12/19/2009
4/13/2009
8/18/2007
7/17/2008
6/16/2009
1/14/2009
12/18/2007
9/14/2009
2/13/2006
3/25/2009
2/23/2007
I want convert it and only have the list with month/year if is it possible as dateformat, like this:
我想转换它，如果有可能作为日期格式，则只有带有月/年的列表，如下所示：
10/2009
12/2009
4/2009
8/2007
7/2008
6/2009
1/2009
12/2007
9/2009
2/2006
3/2009
2/2007
回答by jezrael
I think you can use first to_datetimeand then to_period:
我认为你可以先使用to_datetime，然后to_period：
df.col = pd.to_datetime(df.col).dt.to_period('m')
print (df)
col
0 2009-10
1 2009-12
2 2009-04
3 2007-08
4 2008-07
5 2009-06
6 2009-01
7 2007-12
8 2009-09
9 2006-02
10 2009-03
11 2007-02
print (type(df.loc[0,'col']))
<class 'pandas._period.Period'>
Or strftime:
或strftime：
df.col = pd.to_datetime(df.col).dt.strftime('%m/%Y')
print (df)
col
0 10/2009
1 12/2009
2 04/2009
3 08/2007
4 07/2008
5 06/2009
6 01/2009
7 12/2007
8 09/2009
9 02/2006
10 03/2009
11 02/2007
print (type(df.loc[0,'col']))
<class 'str'>
Or replaceby regex:
或replace通过regex：
df.col = df.col.str.replace('/.+/','/')
print (df)
col
0 10/2009
1 12/2009
2 4/2009
3 8/2007
4 7/2008
5 6/2009
6 1/2009
7 12/2007
8 9/2009
9 2/2006
10 3/2009
11 2/2007
print (type(df.loc[0,'col']))
<class 'str'>
回答by EdChum
回答by internetional
Or you could use a regular expression, if you prefer that kind of solution. This would solve your problem:
或者您可以使用正则表达式，如果您更喜欢那种解决方案。这将解决您的问题：
import re
res = re.sub(r"/\d\d?/", "/", s)
(Note that sis the date string, either as separate date strings or a long string containing all dates, and that you have your result bound to res.)
（请注意，这s是日期字符串，可以是单独的日期字符串，也可以是包含所有日期的长字符串，并且您的结果绑定到res.）
