In addition to the Python syntax, Yanaconda supports the C-like do .. while X style. In the latter case, the loop is run at least once, even if the expression at the end is false.

i = 3
while i<50
  Print (i)
  i = i*2

3
6
12
24
48

i = 60
do
  Print (i)
  i = i*2
while i<50

60