January 2018 – Eric Lapouyade Info

How to get Class attributes order

Eric / January 29, 2018

Before python 3.6 it was difficult to get attributes order from a class. Let’s say, for instance, you want to create a listing class which contains columns to display :

class Column(object):
  pass

class Listing(object):
  col1 = Column()
  col2 = Column()
  col3 = Column()
  col4 = Column()
  col5 = Column()
  col6 = Column()


print( [ k for k in Listing.__dict__.keys() if '__' not in k ] )

class Column(object):

pass

class Listing(object):

col1 = Column()

col2 = Column()

col3 = Column()

col4 = Column()

col5 = Column()

col6 = Column()

print( [ k for k in Listing.__dict__.keys() if '__' not in k ] )

With python 2.7 you will get :

['col6', 'col4', 'col5', 'col2', 'col3', 'col1']

1	['col6', 'col4', 'col5', 'col2', 'col3', 'col1']

With python 3.5 you will get :

['col3', 'col1', 'col4', 'col5', 'col2', 'col6']

1	['col3', 'col1', 'col4', 'col5', 'col2', 'col6']

And finally, with python 3.6, there is no problem any more : attributes…

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Python

How to dynamically create a class with some mixins

Eric / January 24, 2018

Let’s say you want to create a class that includes mixins having names that are known at execution time only, you would do some thing like this :

class_with_mixins = type("my_class_name", tuple(mixins_classes+[BaseClass]), {})

1	class_with_mixins = type("my_class_name", tuple(mixins_classes+[BaseClass]), {})

To get mixins_classes, juste use importlib to get mixins classes from names. A function that would create an instance of such a dynamic class would be something like this :

from importlib import import_module

def get_instance_with_mixins(plugin_class_name,mixins_name,base_class,*args,**kwargs):
    mixins_classes = [ import_module(m) for m in mixins_name ]
    cls = type(plugin_class_name, tuple(mixins_classes+[base_class]), {})
    instance = cls(*args,**kwargs)
    return instance

from importlib import import_module

def get_instance_with_mixins(plugin_class_name,mixins_name,base_class,*args,**kwargs):

mixins_classes = [ import_module(m) for m in mixins_name ]

cls = type(plugin_class_name, tuple(mixins_classes+[base_class]), {})

instance = cls(*args,**kwargs)

return instance

…

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Android

Android splash screen

Eric / January 12, 2018

There is 2 ways (at least) to create a splash screen : The first is to create a splash activity displaying a layout and then transfert the user to the main activity. Here the SplashActivity.java :

public class SplashActivity extends AppCompatActivity {

    private static int SPLASH_DURATION = 2000;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.splash_activity);
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                Intent intent = new Intent(SplashActivity.this, MainActivity.class);
                startActivity(intent);
                finish();
            }
        },SPLASH_DURATION);
    }
}

public class SplashActivity extends AppCompatActivity {

private static int SPLASH_DURATION = 2000;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.splash_activity);

new Handler().postDelayed(new Runnable() {

@Override

public void run() {

Intent intent = new Intent(SplashActivity.this, MainActivity.class);

startActivity(intent);

finish();

}

},SPLASH_DURATION);

}

Note : the splash screen is displayed during 2 seconds (2000 ms) before going to the main activity. You can tune the SPLASH_DURATION…

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