Rethinkdb python handle empty result

Question

What is the best technique with rethinkb and python to deal with empty result. I try this, but catching exceptions is not satisfactory.

@staticmethod
def get_by_mail(mail):
    try:
        return User(
            r.table('users').filter({"mail": mail}).limit(1).nth(0).run()
        )
    except RqlRuntimeError:
        return None

If anyone has tried other techniques, I am very interested. Thanks for your help.

It's not clear what do you want to do in case of rql runtime error. — alko, Dec 04 '13 at 14:13
He search something like that https://github.com/rethinkdb/rethinkdb/issues/362#issuecomment-13749061 — Stéphane Klein, Dec 04 '13 at 14:50

score 3 · Accepted Answer · answered Dec 04 '13 at 17:17

3

The easiest way to deal with this is probably by adding in the element you want back with a union.

r.table('users').filter({"mail": mail}).limit(1).union([{}])[0]

A slightly ugly work around but it should do the trick. I think we should probably extend the default syntax to work with this. I'm going to make an issue for that.

answered Dec 04 '13 at 17:17

Joe Doliner

2,058
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Thank you, I like this one liner. – k3z Dec 04 '13 at 17:50

score 1 · Answer 2 · answered Dec 04 '13 at 16:22

1

That should work

r.table('users').filter({"mail": mail}).do( lambda users:
    r.branch(
        users.count() == 1,
        users.nth(0),
        None
     )
 )

You can also remove the nth(0) and retrieve a cursor and do:

user = None
for i in user:
     user = i
     break # You don't really need to break since there is at most one element

answered Dec 04 '13 at 16:22

neumino

4,342
1
18
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Thank you, I give it a try too – k3z Dec 04 '13 at 17:51

Rethinkdb python handle empty result

2 Answers2