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CS1 Python Subgoals

Section 6.7 While Loops Sentinel

Subgoals for Evaluating a Loop.

  1. Determine Loop Components
    1. Start condition and values
    2. Iteration variable and/or update condition
    3. Termination/final condition
    4. Body that is repeated based on indentation
  2. Trace the loop, writing updated values for every iteration or until you identify the pattern

Subsection 6.7.1

Problem: Given the following code, what is the output if the user enters the values: 10, 15, 20, 25, 30, 35, -1?
print("Enter a negative score to signal the end of input.")
good_scores = 0
score = int(input("Score: "))
while score >= 0:
    if score >= 20:
        good_scores += 1
    score = int(input("Score: "))
print("Number of good scores: ", good_scores)

Subsection 6.7.2 Determine loop components

Starting values:
good_scores = 0
# score will be the integer 10 since that is the first value the user entered
Termination condition: When score is greater than or equal to 0
Body that is repeated based on indentation:
if score >= 20:
    good_scores += 1
score = int(input("Score: "))

Subsection 6.7.3 Trace the loop, writing updated values for every iteration or until you identify the pattern

For every iteration of loop, write down values.
Trace of the loop for the code in the problem
Number of good scores: 4
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