Recursion Fundamentals in Python is an important beginner topic in real Python work.
This lesson keeps the language simple but professional. You will learn what the concept is, why it matters, and how to apply it safely in small projects.
Detailed explanation of Recursion Fundamentals in Python:
1. Understand the smallest version first.
2. Practice with short examples.
3. Observe outputs and errors carefully.
4. Refactor names so code reads like plain English.
5. Repeat with small daily exercises.
Example 1
Basic recursion
1
def factorial(n):
2
if n <= 1:
3
return 1
4
return n * factorial(n-1)
5
6
print(factorial(5))
Run this example, then change one input and observe what changes.
Example 2
Recursion with list sum
1
def sum_list(nums):
2
if not nums:
3
return 0
4
return nums[0] + sum_list(nums[1:])
Run this example, then change one input and observe what changes.
Example 3
Avoid infinite recursion
1
def countdown(n):
2
if n == 0:
3
return
4
print(n)
5
countdown(n-1)
Run this example, then change one input and observe what changes.
Example 4
Iterator with iter()
1
nums = [10, 20, 30]
2
it = iter(nums)
3
print(next(it), next(it))
Run this example, then change one input and observe what changes.
Example 5
Simple generator
1
def squares(n):
2
for i in range(n):
3
yield i * i
4
5
print(list(squares(5)))
Run this example, then change one input and observe what changes.
Example 6
Generator expression
1
evens = (n for n in range(10) if n % 2 == 0)
2
print(list(evens))
Run this example, then change one input and observe what changes.
Example 7
Yield from file lines
1
def read_lines(path):
2
with open(path, 'r', encoding='utf-8') as f:
3
for line in f:
4
yield line.strip()
Run this example, then change one input and observe what changes.
Example 8
Memory-friendly loop
1
for n in range(1_000_000):
2
if n == 3:
3
break
Run this example, then change one input and observe what changes.
Example 9
Manual next() handling
1
gen = (i for i in [1,2])
2
print(next(gen))
3
print(next(gen))
Run this example, then change one input and observe what changes.
Example 10
StopIteration example
1
it = iter([])
2
try:
3
next(it)
4
except StopIteration:
5
print('done')
Run this example, then change one input and observe what changes.
