Question

Are they the same thing????

while len(deque)>0:
    deque.popleft()

while deque:
   deque.popleft()

so basically these two condition loops can avoid poping from empty queue?

Answer 1

They’re the same, but PEP 8 prefers the second version. I’m not convinced that it’s always easier to read though, so use your own judgement.

http://www.python.org/dev/peps/pep-0008/#programming-recommendations

For sequences, (strings, lists, tuples), use the fact that empty sequences are false.

Yes: if not seq:
     if seq:

No: if len(seq)
    if not len(seq)