Use case of python function argument

Question

I have a python function named grids() with keyword self in arguments, and another python function named build_targets(). I want to use gridsize and anchor_vec from grids() to another python function named build_targets(). Both functions are following:

def grids(self, img_size=(608,608), gridsize=(19, 19), device='cpu', type=torch.float32):

    nx, ny = gridsize  # x and y grid size
    self.nx = nx
    self.ny = ny

    if isinstance(img_size, int):
        self.img_size = int(img_size)
    else:
        self.img_size = max(img_size)

    self.stride = self.img_size / max(gridsize)

    yv, xv = torch.meshgrid([torch.arange(ny), torch.arange(nx)])

    self.register_buffer('grid_xy', torch.stack((xv, yv), 2).view((1, 1, ny, nx, 2)).to(device)) 


    self.anchor_vec = self.anchors.to(device) / self.stride
    self.register_buffer('gridsize',torch.Tensor(gridsize).to(device))


def build_targets(model, targets):

    for i in layers_list:
        ng, anchor_vec = gridsize, anchor_vec # from grids()

Is there any way to use gridsize and anchor_vec in build_targets() or how do I call it in build_target() function?

Any comments would be highly appreciated!

self is not a keyword. In your code, it is merely the name of the first argument to your methods. That is the convention in Python, since this argument gets passed the instance when a method is called from an instance. — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Sep 22, 2021 at 8:53
@luigigi, grid() function is not from class. I have been looking for a way to call it inside build_target() function — Heartbeat
– Heartbeat, Commented Sep 22, 2021 at 9:04
if grids() is not a function in a class, why do you have self as first argument? that does not make sense. also the calls self.nx in that method will not work because you try to reference to class variables (unless you pass an object as first argument when calling grids which is very unlikely). you should check out the basics to python classes. you probably want a class with both methods as functions in your class so you can write and access class variables like anchor_vec in your functions. — gbruenjes
– gbruenjes, Commented Sep 22, 2021 at 9:10
@luigigi thanks for your comments. Would you please check the link following [github.com/ming71/yolov3-pytorch/blob/…, there is a function called create_grids() in line 311, I have been trying to use this function but my own way of implementing model. — Heartbeat
– Heartbeat, Commented Sep 22, 2021 at 9:18

AcaNg · Accepted Answer · 2021-09-22 09:20:58Z

It seems like grids() is a method inside a class, then you have 2 choices:

Modify build_targets(), make it a method inside a class by adding self to its arguments:

class SomeClass:
    def grids(...):
        self.gridsize = gridsize # (*)
        #some code

    def build_targets(self, model, targets):
        for i in layers_list:
            ng, anchor_vec = self.gridsize, self.anchor_vec # requires (*)
            # or
            ng, anchor_vec = (self.nx, self.ny), self.anchor_vec # does not requires (*)

Calling:

some_instance.build_targets(some_model, some_targets)

Add more arguments to build_targets():

def build_targets(model, targets, gridsize, anchor_vec):
    for i in layers_list:
        ng, anchor_vec = gridsize, anchor_vec

Calling:

build_targets(some_model, some_targets, (some_instance.nx, some_instance.ny), some_instance.anchor_vec)
# quite long line

By this way, build_targets() is "independent" to the class. Doing this is equivalent to moving build_targets() out of the class.

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