I can't figure out how to look ahead one element in a Python generator. As soon as I look it's gone.
Here is what I mean:
gen = iter([1,2,3])
next_value = gen.next() # okay, I looked forward and see that next_value = 1
# but now:
list(gen) # is [2, 3] -- the first value is gone!
gen = element_generator()
if gen.next_value() == 'STOP':
The Python generator API is one way: You can't push back elements you've read. But you can create a new iterator using the itertools module and prepend the element:
import itertools gen = iter([1,2,3]) peek = gen.next() print list(itertools.chain([peek], gen))