Python Design Patterns – Command
Command Pattern adds a level of abstraction between actions and includes an object, which invokes these actions.
In this design pattern, client creates a command object that includes a list of commands to be executed. The command object created implements a specific interface.
Following is the basic architecture of the command pattern −
How to implement the command pattern?
We will now see how to implement the design pattern.
def demo(a,b,c): print 'a:',a print 'b:',b print 'c:',c class Command: def __init__(self, cmd, *args): self._cmd=cmd self._args=args def __call__(self, *args): return apply(self._cmd, self._args+args) cmd = Command(dir,__builtins__) print cmd() cmd = Command(demo,1,2) cmd(3)
The above program generates the following output −
The output implements all the commands and keywords listed in Python language. It prints the necessary values of the variables.