将对象方法作为对象参数值传递

Question

I made a BetterMarker class that inherits from folium.Marker which is a geographic point object that can be added to a folium.Map object which produces a Leaflet HTML map.

import folium, datetime

class BetterMarker(folium.Marker):

    def __init__(self, latitude, longitude, **kwargs): 
        super().__init__([latitude, longitude], **kwargs)
        self.latitude = latitude

    def north_or_south(self):
        if self.latitude > 0:
            return "North"
        else:
            return "South"

I can now initialize BetterMarker and add its instance to a folium.Map object:

mymap = folium.Map() # Create Map object
bm = BetterMarker(30, 40, popup = "Hi there")
bm.add_to(mymap) # Add BetterMarker object to Map
mymap.save("mymap.html") # Save the map with the marker into HTML

The code above works just fine producing the following map:

However, instead of using the string Hi there in bm = BetterMarker(30, 40, popup = "Hi there") I want to use bm.north_or_south() :

bm = BetterMarker(30, 40, popup = bm.north_or_south())

Of course, the above wouldn't work. The code below would work, but it means initializing the class two times:

bm = BetterMarker(30, 40)
bm = BetterMarker(30, 40, popup = bm.north_or_south())

What's a sane way to do this? What did I do wrong?

Answer 1

updated according to comment

My first attempt didn't fully understand the requirements. I think some of the other answers are on the right track. Here's a way that works:

class BetterMarker(folium.Marker):

    def __init__(self, latitude, longitude, **kwargs):
        if kwargs['popup_method']:
            kwargs['popup'] = kwargs['popup_method'](latitude, longitude, **kwargs)
            del kwargs['popup_method']
        super().__init__([latitude, longitude], **kwargs)

    @staticmethod
    def quadrant(latitude, longitude, **kwargs):
        if latitude > 0 and longitude > 0:
            return "North East"
        elif latitude > 0 and longitude <= 0:
            return "North West"
        elif latitude <= 0 and longitude > 0:
            return "South East"
        else:
            return "South West"

As for calling, it's important to pass only the method and not to call it by including parentheses:

bm = BetterMarker(-30, 40, popup_method=BetterMarker.quadrant)

Notice I made a new keyword parameter called popup_method since popup meant the text. Also, I added longitude and kwargs to the popup method's signature so those methods have access to everything the caller passed.

Answer 2

Relating to comments in question. Something like so:

class Foo:
    def __init__(self, *args, **kwargs):
        self.alert = kwargs['alert']

    def print_alert(self):
        print(self.alert())

class Bar(Foo):
    def __init__(self, *args, **kwargs):
        if "alert" not in kwargs:
            kwargs['alert'] = self.custom_alert() # Notice here.

        super().__init__(*args, **kwargs)

    def custom_alert(self):
        return "Custom Alert"

Bar().print_alert() # >>> Custom Alert

---

Edit

As per the comment below, you could simply define the method(s) as @staticmethod :

class Foo:
    def __init__(self, *args, **kwargs):
        self.alert = kwargs["alert"]

    def print_alert(self):
        print(self.alert()) # Notice we DO call the variable.


class Bar(Foo):
    def __init__(self, *args, **kwargs):
        if "alert" not in kwargs:
            kwargs["alert"] = self.default_alert

        super().__init__(*args, **kwargs)

    @staticmethod
    def default_alert():
        return "Custom Alert!"

    @staticmethod
    def random_alert():
        return "Random Alert!"


a = Bar()
a.print_alert()

b = Bar(alert=Bar.random_alert)  # Notice we do not CALL the method.
b.print_alert()

outputs:

default
rand

Answer 3

[edit] Maybe just pass popup generating function as a keyword parameter?

import folium, datetime

class CustomPopup:
       @staticmethod
       def north_or_south(latitude, longtitude, **kwargs):
        if latitude > 0:
            return "North"
        else:
            return "South" 

        ...other methods

class BetterMarker(folium.Marker):

    def __init__(self, latitude, longitude, **kwargs): 
        self.latitude = latitude
        if 'msg' in kwargs:
             kwargs['popup'] = kwargs['msg'](latitude, longtitude, **kwargs)
        super().__init__([latitude, longitude], **kwargs)


mymap = folium.Map() # Create Map object
bm = BetterMarker(30, 40, msg=CustomPopup.north_or_south)
bm.add_to(mymap) # Add BetterMarker object to Map
mymap.save("mymap.html")

Answer 4

you could try making north_or_south a static method

@staticmethod
def north_or_south(latitude):
    if latitude > 0:
        return "North"
    else:
        return "South"

This makes it runnable from either an object or an object class, but the function itself doesn't know anything about the object it is being run from nor the class, so you can no longer have

self.north_or_south()

as the function doesn't know anything about the object. Instead we pass the latitude as an argument

self.north_or_south(self.latitude)

and voila, it works. The code gets a little longer but the function no longer needs an object from where to be run. So in your problem you would simply have

bm = BetterMarker(30, 40, popup = BetterMarker.north_or_south(40))