(series == x) doesn't always produce a boolean series: bug?

[xdong]

In [2]: a = pandas.Series(['a', nan, 'b'])

In [3]: a == 'a'
Out[3]:
0 True
1 NaN
2 False

There is a NaN in Out[3]. This can't be the desired result because of the following error:

In [4]: b = pandas.Series(['a', 'b', 'c'])

In [5]: (a == 'a') & (b == 'a')
ValueError Traceback (most recent call last)
/home/dong/ in ()
----> 1 (a == 'a') & (b == 'a')

/home/dong/.virtualenv/src/pandas/pandas/core/series.pyc in wrapper(self, other)
143 if isinstance(other, Series):
144 name = _maybe_match_name(self, other)
--> 145 return Series(na_op(self.values, other.values),
146 index=self.index, name=name)
147 elif isinstance(other, DataFrame):

/home/dong/.virtualenv/src/pandas/pandas/core/series.pyc in na_op(x, y)
132
133 if isinstance(y, np.ndarray):
--> 134 result = lib.vec_binop(x, y, op)
135 else:
136 result = lib.scalar_binop(x, y, op)

/home/dong/.virtualenv/src/pandas/pandas/_tseries.so in pandas._tseries.vec_binop (pandas/src/tseries.c:9302)()

ValueError: Does not understand character buffer dtype format string ('?')

BTW for series of dtype float there is no such problem:

In [6]: c = pandas.Series([1.0, nan, 3.0])

In [7]: c == 1
Out[7]:
0 True
1 False
2 False

[adamklein]

Just a heads up that this is under consideration - thanks for bringing to attention.

[wesm]

Looked at this again. Returning boolean array now (comparison with NA -> False)