[python] Python: print a generator expression?

In the Python shell, if I enter a list comprehension such as:

>>> [x for x in string.letters if x in [y for y in "BigMan on campus"]]

I get a nicely printed result:

['a', 'c', 'g', 'i', 'm', 'n', 'o', 'p', 's', 'u', 'B', 'M']

Same for a dictionary comprehension:

>>> {x:x*2 for x in range(1,10)}
{1: 2, 2: 4, 3: 6, 4: 8, 5: 10, 6: 12, 7: 14, 8: 16, 9: 18}

If I enter a generator expression, I get not such a friendly response:

>>> (x for x in string.letters if x in (y for y in "BigMan on campus"))
<generator object <genexpr> at 0x1004a0be0>

I know I can do this:

>>> for i in _: print i,
a c g i m n o p s u B M

Other than that (or writing a helper function) can I easily evaluate and print that generator object in the interactive shell?

Or you can always map over an iterator, without the need to build an intermediate list:

>>> _ = map(sys.stdout.write, (x for x in string.letters if x in (y for y in "BigMan on campus")))
acgimnopsuBM

Unlike a list or a dictionary, a generator can be infinite. Doing this wouldn't work:

def gen():
    x = 0
    while True:
        yield x
        x += 1
g1 = gen()
list(g1)   # never ends

Also, reading a generator changes it, so there's not a perfect way to view it. To see a sample of the generator's output, you could do

g1 = gen()
[g1.next() for i in range(10)]

>>> list(x for x in string.letters if x in (y for y in "BigMan on campus"))
['a', 'c', 'g', 'i', 'm', 'n', 'o', 'p', 's', 'u', 'B', 'M']

You can just wrap the expression in a call to list:

>>> list(x for x in string.letters if x in (y for y in "BigMan on campus"))
['a', 'c', 'g', 'i', 'm', 'n', 'o', 'p', 's', 'u', 'B', 'M']