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What You Will Learn
Beginner
- How range() works (start, stop, step)
- How enumerate() gives index + value
- Common patterns with both
range() - Generate Number Sequences
Terminalpython
range(5) # 0, 1, 2, 3, 4
range(3, 8) # 3, 4, 5, 6, 7
range(0, 10, 2) # 0, 2, 4, 6, 8 (step=2)
range(10, 0, -1) # 10, 9, 8, ..., 1 (countdown!)
# range() is lazy - does not create a list
# Convert to list to see values
print(list(range(5))) # [0, 1, 2, 3, 4]range() is lazy
range() does not create a list in memory. It generates numbers on demand. This is efficient for large ranges like range(1000000).enumerate() - Index and Value Together
Terminalpython
fruits = ["apple", "banana", "cherry"]
# Without enumerate (clunky)
for i in range(len(fruits)):
print(f"{i}: {fruits[i]}")
# With enumerate (Pythonic!)
for i, fruit in enumerate(fruits):
print(f"{i}: {fruit}")
# 0: apple
# 1: banana
# 2: cherry
# Start from a custom index
for i, fruit in enumerate(fruits, start=1):
print(f"{i}: {fruit}")
# 1: apple, 2: banana, 3: cherryCommon Patterns
Terminalpython
# Countdown timer
for i in range(10, 0, -1):
print(f"{i}...")
print("Launch!")
# Sum of 1 to 100
total = sum(range(1, 101))
print(total) # 5050
# Every other element
for i in range(0, 10, 2):
print(i) # 0, 2, 4, 6, 8Practical Exercise
Print 0 to 9 with range(10)
Print 10 to 1 (countdown) with range(10, 0, -1)
Use enumerate to print index: value of ['a', 'b', 'c']
Calculate sum(range(1, 101)) - what is the result?
Key Takeaways
- range(stop): 0 to stop-1.
- range(start, stop, step): custom sequences.
- range() is lazy - efficient for large ranges.
- enumerate() gives index + value - more Pythonic than range(len()).
- enumerate(items, start=1) for 1-based indexing.
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