Python decorators

Why decorators are needed?

Suppose we have two functions(func1, func2). Func1 will print "I'm from func1" and func2 will print "I'm from func2".
Suppose these functions are already created. But after creating the function, now we also want that when each function gives the output that time they also print another thing and that is "This function is very good". But the problem is we already wrote the code and we don't want to do changes inside the code but we also want to add something new.
Now what we will do?
In this case, we will use decorators.

In the example, when we called the decorator function and the decorator function takes a parameter which is the function. So we pass the func1 function as a parameter. So first decorator_func will be called and this function will return another function and that is wraper_function. Now, this wrapper function is stored in var1 and var2 variables. So when we call var1, it means we are calling the wrapper function. So after calling var1 wraper_function will run and first it will print "This function is very good", then it will work with the parameter value. Here we pass a function as a parameter. So when the wrapper function will start working with the parameter it will run the function given in the parameter and will print "I form func1".We always have to return wraper_function and take_function.

Shortcut of decorator

To use the decorators shortcut, we have to write @decorator_function_name before the main function.

In example 1 we have two main functions (func1,func2) and a decorator function. Here we wrote @decorator_func before func1 and func2. By doing this we don't have to create a variable and then call the decorator function and also don't need to pass the main function as a parameter. If we just give the call main function then the decorator main function will automatically execute together and will give the output. If we do this then the first decorator function will execute and then the main function will be executed.

If we want to use parameters and pass a value of the parameter to the main function(func1, func2) then we have to write *args and **kwargs in wrapper function and take_function.