PEP 289: Generator Expressions (please comment)

[Werner Schiendl]

Hi,


Rainer Deyke wrote:

> 
> At the very least, it would require parentheses if you want to create a list
> containing exactly one such generator.
> 
> [(x for x in y)] # List containing generator
> [x for x in y]   # List comprehension
> 
> 

personally the parentheses seem a little strange to me, or put another 
way, I feel that simple parentheses around "everything" should not 
change the meaning of the code.

For example, see current tuple syntax:

 >>> def p(x):
... 	print type(x)
... 	
 >>> p(5)
<type 'int'>
 >>> p((5))
<type 'int'>
 >>> p((5,))
<type 'tuple'>


As the code shows, just putting parentheses around the value 5 doesn't 
make it a tuple.


Another point is that I think it's one of Python's advantages to not 
require extensive parentheses e. g. for 'if' 'while' 'for' etc.

Unlike in C you can just write

if a > 7:
      print "Large enough."


So requiring parentheses around the only item for a list with one 
generator in it seems a little inconsistent in my eyes.

Maybe an alternative would be to have similar to tuples:

[x for x in y, ] # List containing generator
[x for x in y]   # List comprehension


Just my 2c

Werner