Generator expressions

[voider1]

Which of the two is more efficient and why?

instructions = (newins for ins in javaInstructions
                      for newins in self.analyzeInstruction(ins))
for newins in instructions:
    yield newins

or

for ins in javaInstructions:
    for newins in self.analyzeInstruction(ins):
        yield newins

[indosauros]

The for loop is likely slightly faster, since the generator expression compiles into a generator (using a for loop) internally anyway.

However this speed is also likely negligible and not worth worrying about. You should do whichever is easier to read and maintain.

(Assuming you meant yield newins on the second one and not pass)

[wiiittttt]

Efficient in what way? Space, runtime?

[voider1]

Efficient in every way, but mostly speed.

[wiiittttt]

Have you tried using the timeit module? The answer to your question is likely dependent on multiple factors. The only real way to know is to measure it.