Running functions from a list issue

Question

I am wondering how to run functions from a list, and calling them using the random module, but I can't seem to get it to work can anyone help? Here is an example below.

import random
def word1():
       print "Hello"
def word2():
       print "Hello again"

wordFunctList = [word1, word2]

def run():
       printWord = random.randint(1, len(wordFunctList))-1
       wordFunctList[printWord]
       run()
run()

So I wanted to do this in an infinite loop, but all I get for output is

Hello
Hello again

Then the program just doesn't do anything else? Can anyone help me? Btw, I am using the app pythonista. Also I am a programming NOOB. I just recently started with python.

The whole reason I am asking this question is because I am making a text based world generator, and I want to define functions for biomes, then randomly call them from a list while the world is generating.

This question appears to be off-topic because it is about a problem which is not reproducible. — thefourtheye, Apr 02 '14 at 04:19
I am sure you wouldn't have got the output you mentioned in the question, since you didn't invoke the functions and it is already executed infinitely, and causes stackoverflow — thefourtheye, Apr 02 '14 at 04:20
Well this in my original program I used time.sleep to prevent instantaneous stack overflow — DatEpicCoderGuyWhoPrograms, Apr 02 '14 at 04:22
I just tried it on pythonista again, and I got the same output I mentioned, even with the new suggested method below. I am really starting to think that it is a bug with pythonista. — DatEpicCoderGuyWhoPrograms, Apr 02 '14 at 04:31

score 3 · Accepted Answer · edited May 23 '17 at 10:24

3

I'd do it this way:

import random

def word1():
    print "Hello"

def word2():
    print "Hello again"

wordFunctList = [word1,  word2]

def run():
    # Infinite loop, instead of recursion
    while True:
        # Choose the function randomly from the list and call it
        random.choice(wordFunctList)()

run()

Read this answer. It explains why you should avoid tail recursion and use infinite loop instead.

Explanation on random.choice(wordFunctList)():

wordFunctList is a list with function objects:

>>> print wordFunctList
[<function word1 at 0x7fcb1f453c08>, <function word2 at 0x7fcb1f453c80>]

random.choice(wordFunctList) chooses the function and returns it:

>>> random.choice(wordFunctList)
<function word2 at 0x7f9ce040dc80>

random.choice(wordFunctList)() calls the returned function:

>>> print random.choice(wordFunctList)()
Hello again # Outputs during the function call
None        # Returned value

With extra parentheses (random.choice(wordFunctList)()()), you were calling the returned value of the function, that is None, but None is not callable and that's why you were getting the error.

edited May 23 '17 at 10:24

Community

1
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answered Apr 02 '14 at 04:22

vaultah

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How would I go about choosing the function and calling it, in the same way? Or another way? Because if I am calling the function wrong, I get a TypeError: object not callable – DatEpicCoderGuyWhoPrograms Apr 02 '14 at 04:35
1

@user3487713 if there're only functions in your list, then you can't get `object not callable` error – vaultah Apr 02 '14 at 04:37
The error also said something about a 'NoneType' don't know if that changes anything... – DatEpicCoderGuyWhoPrograms Apr 02 '14 at 04:41
Maybe it's because I accidentally added extra parentheses at the end. And it now seems to be working... – DatEpicCoderGuyWhoPrograms Apr 02 '14 at 04:42
Well, the code is working, so I can now focus on the world generator I am making. – DatEpicCoderGuyWhoPrograms Apr 02 '14 at 04:43
@user3487713 your functions return `None`, `random.choice(wordFunctList)` is a function object, `random.choice(wordFunctList)()` is a NoneType object, calling NoneType object causes error. Hope it's clear now. – vaultah Apr 02 '14 at 04:43
Sorry if this frustrates anyone, but I can do some beginner programming, but the vocabulary used when describing it is complicated for me. – DatEpicCoderGuyWhoPrograms Apr 02 '14 at 04:45
2

@user3487713 updated the answer with extra explanation. You should also accept the answer if you find it helpful **and** comprehensive. – vaultah Apr 02 '14 at 04:57
I get it now, I think I just stayed up too late to read it clearly, otherwise, it does make a lot more sense now, thanks for the input on the problem! – DatEpicCoderGuyWhoPrograms Apr 02 '14 at 05:00
How do I accept answers? I just joined stackexchange about 50 minutes ago? I am also running this on a mobile phone. – DatEpicCoderGuyWhoPrograms Apr 02 '14 at 05:16

Running functions from a list issue

1 Answers1