Proposed new syntax

[Marko Rauhamaa]

Ben Finney <ben+python at benfinney.id.au>:

> The Python list comprehension syntax does not specify control flow.

I understand your point, but how do you know your statement is true?

I didn't check this, but I would imagine the list comprehension:

   [ f(x) for x in I if c(x) ]

was defined as syntactic sugar for:

   list(f(x) for x in I if c(x))

where

   f(x) for x in I if c(x)

has heavily iterative semantics.

> List comprehensions, in their syntax, strongly connote a single
> declarative operation. This makes them different from iteration
> syntax.

Except for side effects, you get the same result whichever way you
imagine it.

As a side not, I have found it rather confusing that I have to say:

  [ (x, y) for x in range(5) for y in range(x) ]

instead of:

  [ (x, y) for y in range(x) for x in range(5) ]

After all, you must say:

  [ ((x, y) for y in range(x)) for x in range(5) ]

which, admittedly, means a different thing.


Marko