python: obtaining a column of dates from the columns of years-months-days - python-2.7

Question

Suppose I have a very simple dataframe:
>>> a
Out[158]:
monthE yearE dayE
0 10 2014 15
1 2 2012 15
2 2 2014 15
3 12 2015 15
4 2 2012 15
Suppose that I want to create the column with the date related to every line, using three columns of integers.
When I have simple numbers it is enough to do like:
>>> datetime.date(1983,11,8)
Out[159]: datetime.date(1983, 11, 8)
If I have to create a column of dates (theoretically a very basic request), instead:
a.apply(lambda x: datetime.date(x['yearE'],x['monthE'],x['dayE']))
I obtain the following error:
KeyError: ('yearE', u'occurred at index monthE')

Answer 1

I think you can first remove last char E and then use to_datetime, but then get pandas timestamps not python dates:
df.columns = df.columns.str[:-1]
df['date'] = pd.to_datetime(df)
#if multiple columns filter by subset
#df['date'] = pd.to_datetime(df[['year','month','day']])
print (df)
month year day date
0 10 2014 15 2014-10-15
1 2 2012 15 2012-02-15
2 2 2014 15 2014-02-15
3 12 2015 15 2015-12-15
4 2 2012 15 2012-02-15
print (df.date.dtypes)
datetime64[ns]
print (df.date.iloc[0])
2014-10-15 00:00:00
print (type(df.date.iloc[0]))
<class 'pandas.tslib.Timestamp'>
Thank you MaxU for solution:
df['date'] = pd.to_datetime(df.rename(columns = lambda x: x[:-1]))
#if another columns in df
#df['date'] = pd.to_datetime(df[['yearE','monthE','dayE']].rename(columns=lambda x: x[:-1]))
print (df)
monthE yearE dayE date
0 10 2014 15 2014-10-15
1 2 2012 15 2012-02-15
2 2 2014 15 2014-02-15
3 12 2015 15 2015-12-15
4 2 2012 15 2012-02-15
But if really need python dates add axis=1 to apply, but then is impossible use some pandas functions:
df['date'] =df.apply(lambda x: datetime.date(x['yearE'],x['monthE'],x['dayE']), axis=1)
print (df)
monthE yearE dayE date
0 10 2014 15 2014-10-15
1 2 2012 15 2012-02-15
2 2 2014 15 2014-02-15
3 12 2015 15 2015-12-15
4 2 2012 15 2012-02-15
print (df.date.dtypes)
object
print (df.date.iloc[0])
2014-10-15
print (type(df.date.iloc[0]))
<class 'datetime.date'>