Iteration
Iteration (also known as 'looping') can be used to repeat instructions. There are three types of loops:
post-test loops REPEAT statements UNTIL condition |
pre-tested loops WHILE condition statements ENDWHILE |
counted loops FOR count = startVal TO endVal statements NEXT count ENDFOR |
There is no 'repeat until' loop in Python, because a properly constructed 'while' loop can do the same. The closest to coding a 'repeat until' loop in Python is to use a break
.
From the syllabus: "In Digital Solutions, using BREAK to force exit a loop is considered ineffective because it disrupts loop behaviour and overrides conditions. This also affects maintainability as it impacts the readability of the algorithm or code":
REPEAT UNTIL (post-test loops).py
x = 1 while True: print(x) #body of loop, post-test will execute 1 or more times x = x + 1 if x > 3: #test or control condition comes after execution of loop break
WHILE ENDWHILE (pre-tested loops).py
x = 1 while x <= 3: #test or control condition comes before execution of loop print(x) #body of loop, pre-tested may execute 0 or more times x = x + 1
FOR NEXT ENDFOR (counted loops).py
for x in range(1,4,+1): #controlled looping (start val, stop val, increment val) print(x)