LOOP CHALLENGE

Build the Fibonacci Sequence

Read the expected result and pseudocode first. Then translate the logic into Python.

SCENARIO

Fibonacci Sequence

Each new number is created from the two previous numbers.

EXPECTATION · N = 10

1 1 2 3 5 8 13 21 34 55

CHALLENGE

Write Python code that produces the sequence above when n = 10.

PSEUDOCODE

Think about the flow before syntax

Set N
N ← 10

Prepare the first two numbers
before ← 1, after ← 1

Output the starting values
1, 1

Repeat until N values exist
next ← before + after

Shift the values
before ← after
after ← next

Output next
Continue until count reaches N

○ Not completed

INSTRUCTOR SOLUTION

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n = 10

before = 1
after = 1
count = 2

print(before, end=" ")
print(after, end=" ")

while count < n:
    next = before + after
    before = after
    after = next
    print(next, end=" ")
    count += 1

Instructor note: Focus on the value shift: next = before + after → before = after → after = next.

💻 Fibonacci Lab

Translate the pseudocode into Python

PYTHON CONSOLE

Ready.

MENTAL MODEL

BEFORE

AFTER

NEXT

1 + 1 = 2

Shift → 1, 2 → calculate 3 → shift → calculate 5 → …