Using a dictionary to select function to execute

Simplify, simplify, simplify:

def p1(args):    whateverdef p2(more args):    whatevermyDict = {    "P1": p1,    "P2": p2,    ...    "Pn": pn}def myMain(name):    myDict[name]()

That's all you need.

You might consider the use of dict.get with a callable default if name refers to an invalid function—

def myMain(name):    myDict.get(name, lambda: 'Invalid')()

(Picked this neat trick up from Martijn Pieters)

Simplify, simplify, simplify + DRY:

tasks = {}task = lambda f: tasks.setdefault(f.__name__, f)@taskdef p1():    whatever@taskdef p2():    whateverdef my_main(key):    tasks[key]()

Not proud of it, but:

def myMain(key):    def ExecP1():        pass    def ExecP2():        pass    def ExecP3():        pass    def ExecPn():        pass     locals()['Exec' + key]()

I do however recommend that you put those in a module/class whatever, this is truly horrible.

If you are willing to add a decorator for each function, you can define a decorator which adds each function to a dictionary:

def myMain(key):    tasks = {}        def task(task_fn):        tasks[task_fn.__name__] = task_fn        @task    def ExecP1():        print(1)    @task    def ExecP2():        print(2)    @task    def ExecP3():        print(3)    @task    def ExecPn():        print(4)        tasks['Exec' + key]()

Another option is to place all the functions under a class (or in a different module) and use getattr:

def myMain(key):    class Tasks:        def ExecP1():            print(1)        def ExecP2():            print(2)        def ExecP3():            print(3)        def ExecPn():            print(4)        task = getattr(Tasks, 'Exec' + key)    task()