while loop not looping in python

Question

Simple while loop, not working as expected. I am trying to create a function that will simulate a roll of a die, and keep a running total of the result, until that total is >= m, at which point it should stop. I want to know what the final total is, and how many rolls it took to get there.

Currently it rolls twice, and reports a sum of 9. I have checked the code outside the loop and it does what it should do (that is, these 3 lines: r = rdm.randint(1,6), tot += r, rolls.append(r)).

What am I missing??

def roll(m):
    rolls = []
    tot = 0
    while tot < m:
        r = rdm.randint(1,6)
        tot += r  
        rolls.append(r)
    return tot
    return rolls
    return r

m=100    
roll(m)    
print "The number of rolls was", len(rolls)  
print "The total is", tot

Answer 1

It seems you have a misconception on how control returns from a function and how to return values. The current issue is nothing pertinent to your while loop rather how you are processing returns from a function.

You should understand that there can be multiple return paths but for any particular execution, one and only one return is executed, any subsequent returns in a sequential path is ignored.

Also, you need a way to capture the return values and it cannot automatically pollute your global namespace

So to summarize and solve your problem, a possible way out would be

def roll(m):
    rolls = []
    tot = 0
    while tot < m:
        r = rdm.randint(1,6)
        tot += r  
        rolls.append(r)
    return tot, rolls, r
tot, rolls, r = roll(m) 
print "The number of rolls was", len(rolls)  
print "The total is", tot

Answer 2

This should work in general, but you're using multiple return statements in a row for one function -- that won't work. The moment a function evaluates a return, that function stops firing. If you want to return multiple values, return a tuple:

def roll(m):
    rolls = []
    tot = 0
    while tot < m:
        r = rdm.randint(1,6)
        tot += r  
        rolls.append(r)
    return tot, rolls, r

m=100    
a, b, c = roll(m)    
print "The number of rolls was", len(b)  
print "The total is", a

Answer 3

You can only have to one return statement. Separate your return values with a comma and assign them to variables when you call the function using multiple assignments.

return tot, rolls, r

And when you call the function:

tot, rolls, r = roll(m)