Control Flow and Functions

Learning objectives

A single boundary value changes the decision. Turn a conditional into a function and compare ordinary and boundary inputs.

Conditions and loops

Starting conditions

Scores=[45,60,75,90], and the passing criterion is 60 or higher.

Procedure

1. Use for and if to determine whether each score passes.
2. Implement the same process as pass_flags(scores,threshold) and compare the two results.

Results to retain

• A 4-row table and a reusable function.

scores=[45,60,75,90]
def pass_flags(values,threshold=60):
    return [v>=threshold for v in values]
print(pass_flags(scores))

Record results and self-check

Score:

Loop result:

Function result:

Match:

Points to check

• Did you actually test the boundary value 60?

Changing the Threshold

Starting conditions

Compare passing-student counts and boundary samples at threshold=50,60,80.

Procedure

1. Call pass_flags with each Threshold in $50,60,80$. Keep the four scores unchanged.
2. Tabulate the four pass/fail decisions and the passing-student count for each Threshold. Check whether the comparison operator used when a sample's score equals the Threshold is >=.
3. Identify scores whose decisions changed with the Threshold and explain why.

Results to retain

• A table of decisions and passing-student counts by Threshold.

thresholds=[50,60,80]

Record results and self-check

Threshold:

Decisions for the four scores:

Number of students who pass:

Scores whose decisions changed:

Points to check

• Did you record the decision for a value equal to the cutoff score?

Checking Other Inputs

Starting conditions

Check the function's boundary values using scores [59,60,61] and an empty List.

Procedure

1. Keep Threshold 60 and write the expected function return values for scores [59,60,61] and an empty List before running.
2. Call pass_flags on both inputs and record expected and actual return values side by side. Explain the decision for score 60 and the form of the return value for an empty input.

Results to retain

• Expected and actual return values for both inputs, and an explanation of the boundary value.

# Use the preceding activity's data and functions to check the specified new examples.

Record results and self-check

Input scores:

Prediction before running:

Actual return value:

Boundary value and empty input handling:

Points to check

• Did you run the same function on an empty input too?