Jython (pass float array to java) is there more pythonic way?

Question

I am writing jython application with eclipse SWT/JFace. I have to pass float array to java object to get back some values from it. I am using jarray package for it. Is there more pythonic way to do it?

bounds = zeros(4, 'f')
# from java org.eclipse.swt.graphics.Path.getBounds(float[] bounds)
path.getBounds(bounds)
# from java org.eclipse.swt.graphics.Rectangle(int x, int y, int width,int height)
rect = Rectangle(int(round(bounds[0])), 
                     int(round(bounds[1])),
                     int(round(bounds[2])),
                     int(round(bounds[3])))

Answer 1

Maybe. First, you can reduce the code a bit:

bounds = map(lambda v: int(round(v)), bounds)

This avoids the repeated cast. My next step would be to create a helper method to turn the array into Rectangle, so you don't have to repeat this code:

def toRectangle(bounds):
    bounds = map(lambda v: int(round(v)), bounds)
    return Rectangle(bounds[0], bounds[1], bounds[2], bounds[3])

That would leave you with:

rect = toRectangle(path.getBounds(zeroes(4, 'f'))

Alternatively, create a helper function that directly accepts the path.

Or you could monkey patch Path:

def helper(self):
    bounds = zeros(4, 'f')
    self.getBounds(bounds)
    bounds = map(lambda v: int(round(v)), bounds)
    return Rectangle(bounds[0], bounds[1], bounds[2], bounds[3])

org.eclipse.swt.graphics.Path.toRectangle = helper

rect = path.toRectangle()

Note that this might be slightly wrong. If it doesn't work, look at classmethod() and new.instancemethod() for how to add a method to a class on the fly.

Answer 2

The use of list comprehensions is considered more pythonic these days:

rounded = [int(round(x)) for x in bounds]

This will give you a list of rounded ints. Of course you could assign this to bounds instead of using "rounded"

bounds = [int(round(x)) for x in bounds]

And on our mailing list Charlie Groves pointed out that the whole thing can be exploded with the * operator like this:

rect = Rectangle(*[int(round(x)) for x in bounds])

Answer 3

It's also worth pointing out that there's no need to use zeros to create an array. You can just call getBounds with a Python iterable containing instances that can be converted to the proper type:

path.getBounds([0, 0, 0, 0])