randomly generate n of each of two types

[Alan Isaac]

I need access to 2*n random choices for two types
subject to a constraint that in the end I have
drawn n of each.  I first tried::

def random_types(n,typelist=[True,False]):
    types = typelist*n
    random.shuffle(types)
    for next_type in types:
        yield next_type

This works but has some obvious costs.
To avoid those I considered this instead::

def random_types(n,typelist=[True,False]):
    type0, type1 = typelist
    ct0, ct1 = 0,0
    while ct0+ct1<2*n:
        if random.random() < ((n-ct0)/(2*n-ct0-ct1)):
            next_type = type0
            ct0 += 1
        else:
            next_type = type1
            ct1 += 1
        yield next_type

Does this seem a good way to go?  Comments welcome.

Thank you,
Alan Isaac


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