Filtering out non-readable characters

[Steven Bethard]

Bengt Richter wrote:
> Thanks for the nudge. Actually, I know about generator expressions, but
> at some point I must have misinterpreted some bug in my code to mean
> that join in particular didn't like generator expression arguments,
> and wanted lists.

I suspect this is bug 905389 [1]:

 >>> def gen():
...     yield 1
...     raise TypeError('from gen()')
...
 >>> ''.join([x for x in gen()])
Traceback (most recent call last):
   File "<interactive input>", line 1, in ?
   File "<interactive input>", line 3, in gen
TypeError: from gen()
 >>> ''.join(x for x in gen())
Traceback (most recent call last):
   File "<interactive input>", line 1, in ?
TypeError: sequence expected, generator found

I run into this every month or so, and have to remind myself that it 
means that my generator is raising a TypeError, not that join doesn't 
accept generator expressions...

STeVe

[1] http://www.python.org/sf/905389