Question

我是一名新手编码器，所以请保持温柔。我试图将一个时间戳类型的日期列从Postgres 9数据库（日期在数据库中看起来像这样：2012-03-02 14:25:49）放入rpy2向量中（我使用rpy2）版本2.3.9）然后可以使用ggplot2为图表创建DataFrame。似乎POSIXlt是适当的rpy2数据类型，但也许我错了。我不需要时间，只需要图表的日期。我在Python 2.7中这样做，使用SqlAlchemy 8.3访问数据库的日期列，SQLAlchemy将其转换为Python datetime.datetime格式。日期数据位于＆quot; publish_date＆＃39;列/代码如下。连接和访问数据库似乎工作正常，所以我认为这主要是一个rpy2问题。这是代码：

# PART 0 - Initialize the packages
import sqlalchemy 
from sqlalchemy import *
import rpy2.robjects as robjects
from rpy2.robjects.vectors import DataFrame
from rpy2.robjects.packages import importr
import rpy2.robjects.lib.ggplot2 as ggplot2


# PART 1 - connect to the database
engine = create_engine('postgresql://postgres:pword@localhost/mydb')
metadata = MetaData()
conn = engine.connect()


# PART 2 - ask for stories table
stories = Table('stories', metadata, autoload=True, autoload_with=engine)


# PART 3 - read from that table and populate a new dictionary 
select = sqlalchemy.sql.select

# create dictionary with column names as keys and empty lists of vectors for data
newdict = {
    "stories_id":robjects.IntVector([]),
    "publish_date":robjects.POSIXlt([])
}

# connect to the database, execute a SELECT statement that iterates through table            
# populate the cursor 'row' with data from the table

for row in conn.execute(select([Table('stories', metadata, autoload=True autoload_with=engine)])): 
    newdict["stories_id"] += row.stories_id
    newdict["publish_date"] += row.publish_date

这是我到目前为止运行代码时遇到的错误。

ValueError                                Traceback (most recent call last)
<ipython-input-377-4483b6760461> in <module>()
     50 for row in conn.execute(select([Table('stories', metadata, autoload=True,     autoload_with=engine)])):
     51     newdict["stories_id"] += row.stories_id
 ---> 52     newdict["publish_date"] += row.publish_date
     53 
     54 

/Users/user/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/rpy2-2.3.9-     py2.7-macosx-10.6-x86_64.egg/rpy2/robjects/vectors.pyc in __add__(self, x)
    226 
    227     def __add__(self, x):
--> 228         res = baseenv_ri.get("c")(self, conversion.py2ri(x))
    229         res = conversion.ri2py(res)
    230         return res

/Users/user/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/rpy2-2.3.9-    py2.7-macosx-10.6-x86_64.egg/rpy2/robjects/numpy2ri.pyc in numpy2ri(o)
      59             raise(ValueError("Unknown numpy array type."))
      60     else:
 ---> 61         res = ro.default_py2ri(o)
      62     return res
      63 

 /Users/user/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/rpy2-2.3.9-   py2.7-macosx-10.6-x86_64.egg/rpy2/robjects/__init__.pyc in default_py2ri(o)
    146         res = rinterface.SexpVector([o, ], rinterface.CPLXSXP)
    147     else:
--> 148         raise(ValueError("Nothing can be done for the type %s at the moment." %   (type(o))))
    149     return res
    150 

 ValueError: Nothing can be done for the type <type 'datetime.datetime'> at the moment.

谢谢您提供的任何帮助。我完全失去了。

将Python datetime.datetime对象转换为rpy2日期向量

0 个答案: