Repetition & Iteration (Edexcel GCSE Computer Science): Revision Note

num = 10

while num > 0:

print(num, "...")

num = num - 1

print("Blast off!")

The instructions inside the loop repeat until the num reaches 0

A higher starting number would result in more repeating

print("Do you accept the T&Cs? (Y/N)")

accept = input()

while accept != "Y":

print("Do you accept the T&Cs? (Y/N)")

accept = input()

print("Thank you for accepting the T&Cs")

Whilst the user does not input a "Y" to accept the terms & conditions the question is repeated infinitely

scores = [10, 5, 20, 20, 4, 5, 2, 25, 1]

for i in scores:

print(i * 2)

Outputs the values of the scores array, multiplied by 2 on separate lines

students =[

[1,"Bob",78],

[2,"Fred",24],

[3,"Julie",32]]

for student in students:

print ("Name:",

student[1],

"Test score:",

student[2])

The for loop processes each student in the students table.

In each loop the individual fields are outputted.

The output from this loop is:

Name: Bob Test score: 78

Name: Fred Test score: 24

Name: Julie Test score: 32

Count-controlled

The number of loops is already known or can be determined before the loop starts

Condition-controlled

The number of loops is not known, it continues until the condition is True

choice = "Y"

while (choice != "N"):

choice = input("choose: ")

Repetition

Condition-controlled

count = 0

while (count < 5):

count = count + 1

print (count)

Repetition

Count-controlled

table = ["cat", "dog", "fox"]

for word in table:

print (word)

Iteration

Count-controlled