执行子功能的主功能

Question

I have two functions that accept different parametes:

def foo(name, age):
    pass
def bar(color, shape):
    pass

Now, I have a master function that I want to be able to call with the function I want to execute and it's parameters. Since it's a master function that might call either foo or bar, it's called with only two params (the function to be executed and the parameters for this function.

function is a string telling what function to execute

params will be a dictionary of parameters (like **kwargs)

I can do this to make it work:

def master(function, params):
    if function == 'foo':
        foo(params['name'], params['age'])
    elif function == 'bar':
        foo(params['color'], params['shape'])

And then I call master like:

master('foo',{'name': 'John', 'age': 99})

However if master has a lot of subfuntions to call, there's too much conditions and picking the right parameters for each function.

So I basically have two questions:

1) Instead of calling master with the name of the function and then checking this name in a condition, can I directly pass the function to be executed? If so, how do I execute the function then?

Something like calling master like this:

master(foo(), {'name': 'John', 'age': 99})

2) functions foo and bar don't have **kwargs, however it would be very convinient if I can call them passing just a dictionary and then they assign to each variable their corresponding value from the dict.

So basically, could I do:

params = {'name':'John', 'age':99, 'color':red, 'shape':circle}
foo(params)  # I would like to to this even if foo doesn't have **kwargs
bar(params)  # same for bar

So at the end my ideal call of master would be:

params = {'name':'John', 'age':99, 'color':red, 'shape':circle}

master(foo(), params) # to execute foo
master(bar(), params) # to execute bar

Answer 1

You can pass functions as arguments:

def master(func, arguments: dict):
    if func is foo:
        args = arguments["name"], arguments["age"]
    elif func is bar:
        args = arguments["color"], arguments["shape"]

    return func(*args)

This can be done even simpler if you don't know the names of the functions' arguments:

def master(func, arguments: list):
    return func(*arguments)

A much more generic version is the following:

def master(function, *positional_arguments, **keyword_arguments):
    function(*positional_arguments, **keyword_arguments)

master(foo, 'John', 56)
master(foo, **{'name': 'John', 'age': 56})
master(foo, name='John', age=56)
master(foo, *['John', 56])

Answer 2

function is a first-class object in Python and therefore can be assigned to an identifier, passed as an argument or returned by a function.

The unified way where you don't want to bother of keyword args for a particular function - with inspect.getfullargspec feature:

import inspect

def foo(name, age):
    print(name, age)

def bar(color, shape):
    print(color, shape)

def master(func, params):
    arg_names = inspect.getfullargspec(func).args
    func(**{k:v for k,v in params.items() if k in arg_names})

params = {'name':'John', 'age':99, 'color':'red', 'shape':'circle'}
master(foo, params)
master(bar, params)

Sample output:

John 99
red circle

Answer 3

Function in python are objects, so yes, you can pass them as a parameter (but do not use parenthesis).

def master(function, **kwargs):
    function(params, kwargs)

Then you call the master:

master(foo, name='John', age=99...)

Answer 4

You can execute a function through master function not by passing a function as a parameter inside master, but by passing the definition of the function. Please follow the example below:

   def foo(name, age):
      pass

   def bar(color, shape):
      pass

Now consider a master function:

Func param will contain the defination of the function by adding parentheses after function name, it will make it to execute.

def masterFunc(func, params):
     return func(params)  #  Func param will contain the defination of the function by adding parentheses after function name, it will make it to execute. 

You will use this master function to execute the passed function defination as below:

masterFunc(foo,{a:1}) #Sample execution

Answer 5

In Python, functions are objects, like everything else. You can pass functions as parameters and execute them very simply.

In your case,

 def say_hello(name):
   print "hi ", name

 def say_bye(name, time):
   print name, ", have a good ", time

 say_bye("john", "night")
 john , have a good  night

 def master(fun, **kwargs):
   fun(**kwargs)

 master(say_bye, name='john', time='night')
 john , have a good  night

 params1 = {'name': 'jay', 'time': 'morning'}
 params2 = {'name': 'cole'}

 master(say_hello, **params2)
 hi  cole

 master(say_bye, **params1)
 jay , have a good  morning

this should work.

Answer 6

You can try with the below approach.

Code

class A:
    def a(self, *args, **kwargs):
        print('A')

    def b(self, *args, **kwargs):
        print('B', args, kwargs)

def main(func, *args, **kwargs):
    x = A()
    if hasattr(x, func):
        func = getattr(x, func)
        func(*args, **kwargs)
    else:
        print('No function name {} defined under class'.format(func))


if __name__ == '__main__':
    func = raw_input('Func_name: a/b')
    main(func, (1), {1:1})

Output

~/del$ python test.py 
Func_name: a/ba
True
A
~/del$ python test.py 
Func_name: a/bb
True
('B', (1, {1: 1}), {})
~/del$

Here, we're using getattr function in __builtin__ .
* First it checks whether there's a function/method named a or b under the instance of class A . * If yes, then only it will getattr from it and execute passing the args and kwargs. * If somebody passes function name not defined, it will not crash and return saying the needful statement there.

Hope this helps !