Re-evaluating a function to get a new random value in python

Question

here is the code that I am having a problem with(simplified to make it clearer). It is for a text based game just to help learn things.

class Character(object):
    def __init__(self):
        self.level = 5
        self.moveset = [None,None,None,None] 

    def movesetleveling(self): 
        if self.level > 4:
            self.moveset[0] = Punch(self.level)

def punch(level):
    damagedealt = random.randint(0,5)**level
    return damagedealt

I would like to know how I can make self.moveset[0] = Punch() rather than being equal to the output of Punch() in this block of code. So that everytime i run it in a while loop it will re-evaluate the output of Punch() rather than evaluating Punch() once and assigning that to the 0th index of self.moveset[0].

What do you mean by "run it in a while loop"? How are you intending to use moveset? — BrenBarn
– BrenBarn, Commented Dec 21, 2013 at 6:28
Do you want to have four random punch levels in self.moveset or do you want the first item in self.moveset to be a random punch value in each iteration of your loop? — Burhan Khalid
– Burhan Khalid, Commented Dec 21, 2013 at 6:30
@BrenBarn moveset will be used to show a selection of player moves. they will select a move from the list which will then be evaluated to produce an integer value which will be a damagestat. this damagestat will affect a Foes health. I have created a while loop which does this over and over but each time it uses the same value for self.moveset[0] rather than getting a new value. — Danny Herbert
– Danny Herbert, Commented Dec 21, 2013 at 6:36
@BurhanKhalid i want the first item to be a random punch value in each iteration of the loop. — Danny Herbert
– Danny Herbert, Commented Dec 21, 2013 at 6:43

jfs · Accepted Answer · 2013-12-21 06:45:25Z

2

You could assign a function to self.moveset[0] instead of its result (using functools.partial()):

from functools import partial

self.moveset[0] = partial(punch, self.level)

Then later, in your while loop, just call it:

while True:
    new_punch_every_time = self.moveset[0]() #note: parentheses

self.moveset[0]() calls punch function with level parameter set to self.level (its value at the time of partial call).

It works because functions, methods are first class citizens in Python. You can pass them as parameters to other functions, return from functions, bind to a different name, append to a list, etc.

edited Dec 21, 2013 at 6:45

answered Dec 21, 2013 at 6:32

jfs

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7 Comments

thefourtheye Over a year ago

partial? to a beginner? ;)

jfs Over a year ago

@thefourtheye: OP explicitly said: "to help learn things". functools.partial() is the thing to learn. It is not a crocodile; it won't eat you if you come near it.

Burhan Khalid Over a year ago

Nice, but I suspect the problem might be in the while loop (of the original question)

Danny Herbert Over a year ago

@J.F.Sebastian just had a look at the functools docs and i somewhat agree with @thefourtheye 's sentiment. my head is swimming. A slightly more beginner friendly answer would be greatly appreciated if you know of one!

jfs Over a year ago

@user3124704: which concept/word do you not understand in this sentence: "self.moveset[0]() calls punch function with level parameter set to self.level (its value at the time of the partial call)."? Do you know what function is? What is function parameter? What does it mean to call a function with a given parameter?

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