Arithmetic in pandas HDF5 queries - pandas

Question

Why am I getting an error when I try to do simple arithmetic on constants in an HDF5 where clause? Here's an example:
>>> import pandas
>>> import numpy as np
>>> d = pandas.DataFrame({"A": np.arange(10), "B": np.random.randint(1, 100, 10)})
>>> store = pandas.HDFStore('teststore.h5', mode='w')
>>> store.append('thingy', d, format='table', data_columns=True, append=False)
>>> store.select('thingy', where="B>50")
A B
0 0 61
1 1 63
6 6 80
7 7 79
8 8 52
9 9 82
>>> store.select('thingy', where="B>40+10")
Traceback (most recent call last):
File "<pyshell#26>", line 1, in <module>
store.select('thingy', where="B>40+10")
File "c:\users\brenbarn\documents\python\extensions\pandas\pandas\io\pytables.py", line 682, in select
return it.get_result()
File "c:\users\brenbarn\documents\python\extensions\pandas\pandas\io\pytables.py", line 1365, in get_result
results = self.func(self.start, self.stop, where)
File "c:\users\brenbarn\documents\python\extensions\pandas\pandas\io\pytables.py", line 675, in func
columns=columns, **kwargs)
File "c:\users\brenbarn\documents\python\extensions\pandas\pandas\io\pytables.py", line 4006, in read
if not self.read_axes(where=where, **kwargs):
File "c:\users\brenbarn\documents\python\extensions\pandas\pandas\io\pytables.py", line 3212, in read_axes
self.selection = Selection(self, where=where, **kwargs)
File "c:\users\brenbarn\documents\python\extensions\pandas\pandas\io\pytables.py", line 4527, in __init__
self.condition, self.filter = self.terms.evaluate()
File "c:\users\brenbarn\documents\python\extensions\pandas\pandas\computation\pytables.py", line 580, in evaluate
self.condition = self.terms.prune(ConditionBinOp)
File "c:\users\brenbarn\documents\python\extensions\pandas\pandas\computation\pytables.py", line 122, in prune
res = pr(left.value, right.prune(klass))
File "c:\users\brenbarn\documents\python\extensions\pandas\pandas\computation\pytables.py", line 118, in prune
res = pr(left.value, right.value)
File "c:\users\brenbarn\documents\python\extensions\pandas\pandas\computation\pytables.py", line 113, in pr
encoding=self.encoding).evaluate()
File "c:\users\brenbarn\documents\python\extensions\pandas\pandas\computation\pytables.py", line 317, in evaluate
raise ValueError("query term is not valid [%s]" % self)
ValueError: query term is not valid [[Condition : [None]]]
Querying directly on the underlying pytables object seems to work:
>>> for row in store.get_storer('thingy').table.where("B>40+10"):
... print(row[:])
(0L, 0, 61)
(1L, 1, 63)
(6L, 6, 80)
(7L, 7, 79)
(8L, 8, 52)
(9L, 9, 82)
So what is going on here?

Answer 1

This is simply not supported. I suppose it could fail with a slightly better message. it is trying to and the 2 nodes (the comparison and the +10) and doesn't know how to deal with it as it's not a comparison operation.
I suppose it could be implemented but IMHO is needlessly complex