yield break in Python

Question

According to answer to this question, yield break in C# is equivalent to return in Python. In the normal case, return indeed stops a gener

Answer 1

def generate_nothing():
    return iter([])

Answer 2

A good way to handle this is raising StopIteration which is what is raised when your iterator has nothing left to yield and next() is called. This will also gracefully break out of a for loop with nothing inside the loop executed.

For example, given a tuple (0, 1, 2, 3) I want to get overlapping pairs ((0, 1), (1, 2), (2, 3)). I could do it like so:

def pairs(numbers):
    if len(numbers) < 2:
        raise StopIteration

    for i, number in enumerate(numbers[1:]):
        yield numbers[i], number

Now pairs safely handles lists with 1 number or less.

Answer 3

def generate_nothing():
    return
    yield

Answer 4

The funny part is that both functions have the same bytecode. Probably there's a flag that sets to generator when bytecode compiler finds the yield keyword.

>>> def f():
...   return

>>> def g():
...   if False: yield 
#in Python2 you can use 0 instead of False to achieve the same result


>>> from dis import dis
>>> dis(f)
2           0 LOAD_CONST               0 (None) 
            3 RETURN_VALUE
>>> dis(g)
2           0 LOAD_CONST               0 (None) 
            3 RETURN_VALUE