Going through this tutorial about blaze, but using the iris dataset in a local postgresql db.
I dont seem to get the same output as shown when using db.iris.Species.distinct() (see In 16 of the Ipython notebook).
My connection string is postgresql://postgres:postgres@localhost:5432/blaze_test
and my simple Python code is:
import blaze as bz
db = bz.Data('postgresql://postgres:postgres@localhost:5432/blaze_test')
mySpecies = db.iris_data.species.distinct()
print mySpecies
All I get in the console (using the Spyder IDE) is distinct(_55.iris_data.species)
How can actually print the distinct species in the table?
NB:I know I am using lowercase "s" for the "species" part in the code, otherwise I just get an error to say: 'Field' object has no attribute 'Species'
The printing mechanism is tripping you up a bit here.
The __str__ implementation (which is what Python's print function calls) returns a string version of the expression.
The __repr__ implementation (called when you execute a line in the interpreter) triggers computation and thus allows you to see the results of a computation.
In [2]: iris = Data(odo(os.path.abspath('./blaze/examples/data/iris.csv'), 'postgresql://localhost::iris'))
In [3]: iris
Out[3]:
sepal_length sepal_width petal_length petal_width species
0 5.1 3.5 1.4 0.2 Iris-setosa
1 4.9 3.0 1.4 0.2 Iris-setosa
2 4.7 3.2 1.3 0.2 Iris-setosa
3 4.6 3.1 1.5 0.2 Iris-setosa
4 5.0 3.6 1.4 0.2 Iris-setosa
5 5.4 3.9 1.7 0.4 Iris-setosa
6 4.6 3.4 1.4 0.3 Iris-setosa
7 5.0 3.4 1.5 0.2 Iris-setosa
8 4.4 2.9 1.4 0.2 Iris-setosa
9 4.9 3.1 1.5 0.1 Iris-setosa
...
In [4]: iris.species.distinct()
Out[4]:
species
0 Iris-versicolor
1 Iris-virginica
2 Iris-setosa
In [8]: print(str(iris.species.distinct()))
distinct(_1.species)
In [9]: print(repr(iris.species.distinct()))
species
0 Iris-versicolor
1 Iris-virginica
2 Iris-setosa
If you want to shove the result into a concrete data structure like a pandas.Series, do this:
In [5]: odo(iris.species.distinct(), pd.Series)
Out[5]:
0 Iris-versicolor
1 Iris-virginica
2 Iris-setosa
Name: species, dtype: object