Query for list of attribute instead of tuples in SQLAlchemy
When passing in ORM-instrumented descriptors such as a column, each result is a named tuple, even for just one column. You could use the column name in a list comprehension to 'flatten' the list (you can drop the .all()
call, iteration retrieves the objects too):
result = [r.id for r in session.query(MyModel.id)]
or use the fact that it's a tuple when looping a for
loop and unpack it to a single-element tuple of targets:
result = session.query(MyModel.id)
for id, in result:
# do something with the id
The latter could also be used in a list comprehension:
[id for id, in session.query(MyModel.id)]
You don't really have any options to force the row results to be just the single id
value.
It's strange that SQLalchemy is not providing a proper solution. In sqlalchemy if select a member variable such as a column then each result is a named tuple as @Martijn said. I came to a solution for this using zip function of python
ZIP Method
Zip official docuementation
zip(seq1 [, seq2 [...]]) -> [(seq1[0], seq2[0] ...), (...)] Return a list of tuples, where each tuple contains the i-th element from each of the argument sequences. The returned list is truncated in length to the length of the shortest argument sequence.
Coming to your example
result = session.query(MyModel.id).all()
result = zip(*result)[0]
Output:
[id1, id2, id3...]
How it will work it will flatten list of tuples given as argument if you pass the list like
[(key11, key21), (key12,key22)]
Zip will convert this list of tuples into
[(key11, key12), (key21, key22)]
In your case you want every Initial value of tupe that is of the MyModel so you can take the 0th tuple from the list.
Chain Method
from itertools import chain
result = session.query(MyModel.id).all() # result [(id1,), (id2,), (id3,)]
result = list(chain(*result))
Output
[id1, id2, id3]
For loop
result = session.query(MyModel.id).all() # result [(id1,), (id2,), (id3,)]
result = [id for id, in result]
Output
[id1, id2, id3]