28.02.18 16:56, Chris Angelico пише:
def g(): for x in range(5): y = f(x) yield [y, y] stuff = list(g)
You're not the first to mention this, but I thought it basically equivalent to the "expand into a loop" form. Is it really beneficial to expand it, not just into a loop, but into a generator function that contains a loop?
It is slightly faster (if the list is not too small). It doesn't leak a temporary variable after loop. And in many cases you don't need a list, an iterator would work as well. In these cases it is easy to just drop calling list().
Doesn't leak a temporary? In Python 3, the list comp won't leak anything, but the function is itself a temporary variable with permanent scope. You're right about the generator being sufficient at times, but honestly, if we're going to say "maybe you don't need the same result", then all syntax questions go out the window :D
Explicit for loop leaks variables x and y after the loop. They can hold references to large objects. The generator function itself doesn't hold references to the proceeded data.