PythonCác built-ins quan trọng để xử lý collections hiệu quả:
python
# enumerate — loop có index
fruits = ["apple", "banana", "cherry"]
for i, fruit in enumerate(fruits, start=1):
print(f"{i}. {fruit}")
# zip — gộp nhiều iterables song song
names = ["Alice", "Bob"]
scores = [95, 87]
for name, score in zip(names, scores):
print(f"{name}: {score}")
# map — transform mỗi element (lazy)
doubled = list(map(lambda x: x * 2, [1, 2, 3])) # [2, 4, 6]
# Prefer list comprehension: [x*2 for x in [1,2,3]]
# filter — lọc elements (lazy)
evens = list(filter(lambda x: x % 2 == 0, range(10)))
# Prefer: [x for x in range(10) if x % 2 == 0]Lưu ý: map và filter trả về lazy iterators — cần list() để materialize.
Modern Python ưu tiên list comprehension hơn map/filter vì dễ đọc hơn.
Essential built-ins for working with collections:
python
# enumerate — loop with index
for i, item in enumerate(["a", "b", "c"], start=1):
print(i, item)
# zip — iterate multiple iterables in parallel
for name, score in zip(names, scores):
print(f"{name}: {score}")
# map — transform each element (lazy iterator)
squares = list(map(lambda x: x**2, range(5))) # [0, 1, 4, 9, 16]
# Modern: [x**2 for x in range(5)]
# filter — keep elements matching condition (lazy)
evens = list(filter(lambda x: x % 2 == 0, range(10)))
# Modern: [x for x in range(10) if x % 2 == 0]Pitfall: map and filter return lazy iterators — call list() to materialize.
Prefer list comprehensions for readability.