[Tutor] raw_input and converting string to digit

[Mic Forster]

Hi Guys,

The purpose of this script is to obtain an expected
species-abundance curve given an observed curve. The
script works fine for this purpose but it is
cumbersome to implement. What I am trying to do is to
open this file, enter in a number that represents the
fundamental biodiversity number (theta) and another
that represents the community size (jM), let the
program do its stuff and then give the expected
abundance output. 

I am unsure of the correct syntax to convert a string
from raw_input into a digit. Here is what I have (any
additional comments on any aspect of this code is more
than welcome):

>>>from random import random as rnd

>>>theta = []

>>>def addTheta():
	   theta.append(raw_input(‘Fundamental biodiversity
number is: ‘))

>>>jM = []

>>>def addJM:
	   jM.append(raw_input(‘The metacommmunity size is:
‘))

>>>class growList(list):
        '''A list that does as in Perl: Grows when
        we assign to new indices. I.e. x[1] = 5 will
        work if x was previously empty.'''
        def __setitem__(self, i, val):
            while i >= len(self):
                self.append(None)
            list.__setitem__(self, i, val)
        def __getitem__(self, i):
            'Return 0 for unused slots'
            if i < len(self):
                return list.__getitem__(self, i)
            else:
                return 0

>>>abund = growList()
>>>abund[1] = 1
>>>cumul = growList()

>>>def nsp():
     '''Number of species must be the same as the size
of the abundence list (I guess). Note that first
position is unused to match the 1-based algorithm
syntax.'''
        return len(abund) - 1

>>>for j in range(2, jM + 1):
        x = rnd()
        if x < (theta / float(theta + j - 1)):
            abund.append(1)
        else:	
            cumul[1] = abund[1] / float(j-1)
            for i in range(2, nsp()+1):
                cumul[i] = cumul[i-1] + abund[i] /
float(j-1)
            i = 1
            while x >= cumul[i]:
                i += 1
            abund[i] += 1

>>>for abundance in zip(abund):
  	   print '%s' % abundance


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