While ループ

開発者のためのPython入門

Jasmin Ludolf

Senior Data Science Content Developer

if文

Flow of an if statement: start > condition met > perform action > exit

if文 vs. whileループ

if文

Flow of an if statement: start > condition met > perform action > exit

Whileループ

Flow of a while loop: start > condition met > perform action > loop > repeat until condition is no longer met

Whileループ

while condition:
    action

任意の連続タスク
- ボタンが押されている間（while）は加速する

Games console with a racing game

¹ https://unsplash.com/@joaoscferrao

Whileループ

ingredients_to_add = 5
items_added = 0

# Keep adding while we have items left
while items_added < ingredients_to_add:

    items_added += 1
    remaining = ingredients_to_add - items_added
    print(remaining, "ingredients left to add")

出力

4 ingredients left to add
3 ingredients left to add
2 ingredients left to add
1 ingredients left to add
0 ingredients left to add

items_added が ingredients_to_addに等しくなるとループは終了する

注意事項

条件が満たされている間、while は継続的に実行される

ingredients_to_add = 5
items_added = 0

while items_added < ingredients_to_add:
    remaining = ingredients_to_add - items_added
    print(remaining, "ingredients left")

永遠に実行される

ingredients_to_add = 5
items_added = 0

# INFINITE LOOP - never exits!
while items_added < ingredients_to_add:
    remaining = ingredients_to_add - items_added
    print(remaining, "ingredients left")
    # Forgot to increment items_added!

条件は決して偽にならない
ループが永遠に実行され、プログラムがフリーズする
開発上のよくあるミス

ループの中断

while items_added < ingredients_to_add:
    remaining = ingredients_to_add - items_added
    print(remaining, "ingredients left")


    # Terminate the loop
    break

break は for ループでも使用可能
すでにコードが実行中の場合: Control + C / Command + C

while ループ内の条件文

ingredients_to_add = 5
items_added = 0


while items_added < ingredients_to_add:
    items_added += 1
    remaining = ingredients_to_add - items_added

    if remaining > 3:
        print("Several ingredients remaining")

    elif remaining >= 1:
        print("Almost done!")

    else:
        print("Shopping list complete!")

条件文の出力

Several ingredients remaining
Several ingredients remaining
Almost done!
Almost done!
Shopping list complete!

練習してみましょう！

開発者のためのPython入門