Split Loop

有時迴圈一次會做兩件事，只因剛好能同時完成，但這會增加日後修改難度。
拆開迴圈後，我們每次就只需了解要修改的行為即可。

分別考慮重構與優化，先釐清（重構）再優化。
即便最後拆開迴圈成為效能瓶頸，再重新放一起也不難。
迭代串列往往不會成為瓶頸，但拆開迴圈能引導你做出更好優化。

# Before
numbers = [10, 20, 30, 40, 50]
total = 0
count = 0
for number in numbers:
    total += number
    count += 1
average = total / count
print(f"Total: {total}, Average: {average}")

# After
numbers = [10, 20, 30, 40, 50]
total = 0
count = 0

for number in numbers:
    total += number

for number in numbers:
    count += 1

average = total / count
print(f"Total: {total}, Average: {average}")