README.md

Collection of some advanced skills while using python

decoeator

A function of function. Modify the behavior of a function, e.g. add new properties, without changing the function itself. See script test_decorator.py

classmethod

The function decorated by @classmethod does not need to be instantiated and does not need a self parameter.

The first parameter needs to be the cls parameter representing its own class, which can be used to call class attributes, class methods, instantiated objects, etc. See script use_classmethod.py

cls: represents the outer class itself, which can be instantiated or directly call static methods, class methods, and static variables.

• To call a classmethod, the general form is: class_name.classmethod_name(). For example,

class Link:
    '''
        Robot link
    '''
    def __init__(self, length: float, mass: float):
        self.mass = mass
        self.length = length

    @classmethod
    def copy_from_link(cls, link):
        return cls(link.length, link.mass)
    

if __name__ == '__main__':
    link1 = Link(0.5, 1.0)
    link2 = Link.copy_from_link(link1)
    link3 = link1.copy_from_link(link1) # not recommend
    

Also, we can instantiate a class object and call the class method using this object, which is not recommended.

• To call static variable Two ways:

# way one
class_name.variable_name
# way two
cls.variable_name

• To call other class methods/static methods inside classmethods

cls.classmethod_name()
cls.staticmethod_name()

• To call common methods inside classmethods to access instance properties. You need to instantiate a class object through the cls variable, and then use this object to call common methods and the instance's properties.

cls().method_name()

dataclass

MultiProcess

• See script multi_process.py for a simple sample code;
• For communications with Pipe between two processes, see multi_process_com.py;
• For communications with Queue between multiple processes, see multi_process_com2.py