piping data stream through GPG

[robert]

I played around trying to encrypt/decrypt data through GPG on the 
fly (or worse - by using a file) (on Windows first - later to try 
on Linux too)

Using os.popen3 like

 >>> i,o,e=os.popen3('gpg -e -r Robert')
 >>> # i.write('y\n')
 >>> i.write('wefwef')
 >>> i.close()
 >>> # e.read(1)
 >>> o.read(1)

hangs on o.read or e.read.

So its quite dark. Just a totally non-existing userid (-r) will 
result significantly different like

 >>> i.write('wefwef')
Traceback (most recent call last):
   File "<interactive input>", line 1, in ?
IOError: [Errno 22] Invalid argument


GPG asks confirmation stuff (and pwd upon -d or -c) on the command 
line.
How to get all this the right way?


Robert