Generate a sequence of random numbers that sum up to 1?

[Edward Elliott]

Anthony Liu wrote:
 > But, I want the random numbers just generated sum up
 > to 1 .

This seems like an odd request.  Might I ask what it's for?

Generating random numbers in [0,1) that are both uniform and sum to 1 looks 
like an unsatisfiable task.  Each number you generate restricts the 
possibilities for future numbers.  E.g. if the first number is 0.5, all 
future numbers must be < 0.5 (indeed, must *sum* to 0.5).  You'll end up 
with a distribution increasingly skewed towards smaller numbers the more 
you generate.  I can't imagine what that would be useful for.

If that's not a problem, do this: generate the numbers, add them up, and 
divide each by the sum.

nums = [random.uniform(0,1) for x in range(0,100)]
sum = reduce(lambda x,y: x+y, nums)
norm = [x/sum for x in nums]

Of course now the numbers aren't uniform over [0,1) anymore.

Also note that the sum of the normalized numbers will be very close to 1, 
but slightly off due to representation issues.  If that level of accuracy 
matters, you might consider generating your rands as integers and then 
fp-dividing by the sum (or just store them as integers/fractions).