List Patterns

This lesson teaches list patterns you will use in real projects.

1) Build a list from data

nums = []
for i in range(5):
    nums.append(i*i)
print(nums)

Better with comprehension:

nums = [i*i for i in range(5)]

2) Flatten a list of lists

data = [[1,2], [3,4], [5]]
flat = [x for row in data for x in row]
print(flat)

3) Chunk a list (split into parts)

items = list(range(10))
size = 3

chunks = [items[i:i+size] for i in range(0, len(items), size)]
print(chunks)

4) Remove items safely while looping (important)

Wrong way:

# can skip items

Right way:

nums = [1,2,3,4,5,6]
nums = [n for n in nums if n % 2 == 1]
print(nums)

Graph: chunking

flowchart LR
  A[0..9] --> B[0..2]
  A --> C[3..5]
  A --> D[6..8]
  A --> E[9]

Remember

• Comprehensions are powerful and readable
• Avoid modifying list while iterating
• Chunking and flattening are common tasks