Generate a Fibonacci series using a loop in Python
🔢 What is the Fibonacci Series?
The Fibonacci series is a sequence of numbers where:
F(0) = 0
F(1) = 1
F(n) = F(n-1) + F(n-2)So the series is:
0, 1, 1, 2, 3, 5, 8, 13, 21, ...✅ Python Code Using Loop
# Number of terms
n = 10
# First two terms
a = 0
b = 1
# Print Fibonacci sequence
print("Fibonacci series up to", n, "terms:")
for i in range(n):
print(a, end=' ')
# Next number = sum of previous two
c = a + b
a = b
b = c🧠 Explanation (Step-by-step)
🔁 Loop-based logic:
- Start with
a = 0,b = 1(first 2 terms). - Loop
ntimes. - In each iteration:
- Print current value
a. - Calculate next term
c = a + b. - Shift values:
a = b,b = cto prepare for next iteration.
- Print current value
🧮 Dry Run Example (n = 5):
| Iteration | a | b | c = a + b | Printed |
|---|---|---|---|---|
| 1 | 0 | 1 | 1 | 0 |
| 2 | 1 | 1 | 2 | 1 |
| 3 | 1 | 2 | 3 | 1 |
| 4 | 2 | 3 | 5 | 2 |
| 5 | 3 | 5 | 8 | 3 |
📚 DSA Concept Behind Fibonacci Series
| Concept | Explanation |
|---|---|
| Data Structure Used | Variables (a, b, c) — constant space. |
| Time Complexity | O(n) — because we loop n times. |
| Space Complexity | O(1) — no extra space is used except 3 variables. |
| Optimization Tip | Using loop is better than recursion (which uses O(2^n) time and stack space). |
🚀 Bonus: Store Fibonacci Series in a List
def fibonacci_list(n):
fib = []
a, b = 0, 1
for _ in range(n):
fib.append(a)
a, b = b, a + b
return fib
print(fibonacci_list(10))
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