4. While loops
4.1. Events as conditions
x = 10
while x > 0 :
print(x)
x = x - 1
x = 10
4.2. Counters
4.3. Counting up
i
is the counter.i
starts off at 0 and is increased by 1 in the while loop line: i += 1
.i += 1
is the same as i = i + 1
i < 10
, is True the while loop runs.i += 1
causes i
to increase from 0 to 9.i
is 10 since i < 10
will be False when i = 10
.i = 0
while i < 10:
print(i)
i += 1
4.4. Counting down
i
starts off at 5 and is decreased by 1 in the while loop line: i -= 1
.i -+= 1
is the same as i = i - 1
>
sign when counting down.i
is no longer greater than 1, i.e. when it is 1.i = 5
while i > 1:
print(i)
i -= 1
4.5. Step size
i += 2
sets a step size of 2.i = 0
while i < 11:
print(i)
i += 2
Tasks
Write a while loop that counts up from 1 to 5, printing the numbers 1, 2, 3, 4, 5.
Write a while loop that counts up from 3 to 12 in steps of 3, printing the numbers 3, 6, 9, 12.
Write a while loop that counts down from 9 to 1, showprintinging the numbers 9, 8, 7, 6, 5, 4, 3, 2, 1.
Write a while loop that counts down from 24 to 18 in steps of 2, printing the numbers 24, 22, 20, 18.
Write 2 while loops to print 0 to 8 going up in 2s then 9 down to 1 going down in 2s.
Write a while loop that counts up from 1 to 5, printing the numbers 1, 2, 3, 4, 5.
i = 1
while i < 6:
print(i)
i += 1
Write a while loop that counts up from 3 to 12 in steps of 3, printing the numbers 3, 6, 9, 12.
i = 3
while i < 13:
print(i)
i += 3
Write a while loop that counts down from 9 to 1, printing the numbers 9, 8, 7, 6, 5, 4, 3, 2, 1.
i = 9
while i > 0:
print(i)
i -= 1
Write a while loop that counts down from 24 to 18 in steps of 2, printing the numbers 24, 22, 20, 18.
i = 24
while i > 17:
print(i)
i -= 2
Write 2 while loops to print 0 to 8 going up in 2s then 9 down to 1 going down in 2s.
i = 0
while i < 9:
print(i)
i += 2
i = 9
while i > 0:
print(i)
i -= 2