[Tutor] Lists of lists - different sized lists

[Kent Johnson]

Adam Cripps wrote:
> I'm trying to sort [1] a list of people randomly into groups. My guess
> is that a list of lists will do the trick here. However, the randrange
> fails with an empty range. How can I check for this? I thought that my
> pupils list wouldn't reach zero with the while len(pupils)>0: would
> keep it above 0.

You don't show the pupilslength() function so I will assume it is just 
returning len(pupils). One problem is if len(pupils) < size you will 
exhaust the pupils list before you fill tmplist. This will happen in the 
inner loop so the test for len(pupils) > 0 will not be reached.

One option would be to test len(pupils) > 0 again in the condition for 
the inner loop.

BTW you can just test 'if pupils:' rather than 'if len(pupils) > 0:'

Kent

> 
> Any help or advice would be appreciated.
> 
> TIA
> Adam
> 
> [1]
> def groups(pupils, size):
>     toplist = []
>     tmplist = []
>     print len(tmplist)
>     while len(pupils)>0:
>         print len(pupils)
>         while len(tmplist)<=size:
>             print "tmplist is ", len (tmplist)
>             #How many pupils are we talking about here?
>             listlength = pupilslength(pupils)
>             rand1 = random.randrange(listlength)
>             tmplist.append(pupils[rand1])
>             pupils.pop(rand1)
>         toplist.append(tmplist)
>         tmplist = []
>     for i in toplist:
>         print i
>         print i