accessing python dict with function values

Question

I am trying to make a menu of options in python where if the user selects a number a different function is executed:

def options(x):
    return {
        1: f1(),
        2: f2()
    }[x]

def f1():
    print "hi"

def f2():
    print "bye"

However, well I call

options(1)

I get:

hi
bye

and same when I call options(2)

What is going on?

Answer 1

You are invoking the functions instead of assiging them against the keys

def f1():
  print "hi"

def f2():
  print "bye"

functions = {1: f1, 2: f2}  # dict of functions (Note: no parenthesis)

def options(x):
    return functions[x]()   # Get the function against the index and invoke it

options(1)
# hi

options(2)
# bye

Answer 2

Your dictionary is built with the return values of the functions; don't call the function until after picking it from the dict:

def options(x):
    return {
        1: f1,
        2: f2
    }[x]()

Now you are storing just a reference to the functions in the dictionary, and call the selected function after retrieving it.

Demo:

>>> def f1():
...     print "hi"
... 
>>> def f2():
...     print "bye"
... 
>>> def options(x):
...     return {
...         1: f1,
...         2: f2
...     }[x]()
... 
>>> options(1)
hi
>>> options(2)
bye

Answer 3

Replace print with return and return with, then it will work. Or use thefourtheye version.

Answer 4

The problem is that you call the functions (with () ) while you are building the dictionary. Leave the parens off and apply them later only after getting the value from the dictionary:

def options(x):
    return {
        1: f1,
        2: f2
    }[x]()