Appending to a python list while iterating on it

notsure

# This seems like a bad idea, but it also seems to work

In [3]: baselist = range(20)

In [4]: baselist
Out[4]: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19]

In [5]: for item in baselist:
   ...:     if item % 2:
   ...:         baselist.append(item + 1)
   ...:     else:
   ...:         print item
   ...: 
0
2
4
6
8
10
12
14
16
18
2
4
6
8
10
12
14
16
18
20

saferqueue

# This is threadsafe and blocking if that's your bag
In [38]: q = Queue.Queue()

In [39]: for i in range(20):
    ...:     q.put(i)
    ...: 

In [40]: while True:
    ...:     if q.empty():
    ...:         break
    ...:     item = q.get()
    ...:     if item % 2:
    ...:         q.put(item + 1)
    ...:     else:
    ...:         print item
    ...: 
0
2
4
6
8
10
12
14
16
18
2
4
6
8
10
12
14
16
18
20