for 迴圈

Python 入門（開發者向）

Jasmin Ludolf

Senior Data Science Content Developer

逐一比較

# Ingredient quantities
quantities = [500, 400, 15, 20, 30, 5]

# Validate values
quantities[0] < 10

False

quantities[1] < 10

False

for 迴圈語法

for value in sequence:
    action

對於 sequence 中每個 value，執行此 action
- 由於前一行有冒號，action 需縮排
sequence = 可疊代物件，如 list、dictionary 等
value = 迭代器，即索引
- 只是佔位名稱（可自訂），常見為 i

逐一列印元素

# Ingredients list
ingredients = ["pasta", "tomatoes", "garlic", "basil", "olive oil", "salt"]


# Loop through and print each ingredient
for ingredient in ingredients:

    print(ingredient)

pasta
tomatoes
garlic
basil
olive oil
salt

for 迴圈中的條件判斷

quantities = [1000, 800, 40, 30, 30, 15]

for qty in quantities:

for 迴圈中的條件判斷

quantities = [1000, 800, 40, 30, 30, 15]

for qty in quantities:

    # Check if quantity is more than 500
    if qty > 500:
      print("Plenty in stock")
    elif qty >= 100:
        print("Enough for a small portion")
    else:
        print("Nearly out!")

for 迴圈中的條件判斷

Plenty in stock
Enough for small
Nearly out!
Nearly out!
Nearly out!

迭代字串

ingredient_name = "pasta"

# Loop through each character
for letter in ingredient_name:
    print(letter)

p
a
s
t
a

適合驗證文字、檢查特殊字元

迭代字典（dictionary）

ingredients = {"pasta": 500, "tomatoes": 400, "garlic": 30}


# Loop through keys and values
for item, qty in ingredients.items():
    print(item, ":", qty, "grams")

pasta : 500 grams
tomatoes : 400 grams
garlic : 30 grams

item = key（食材名稱）
qty = value（數量）

迭代字典（dictionary）

ingredients = {"pasta": 500, "tomatoes": 400, "garlic": 30}
factor = 2

# Calculate scaled quantities
for item, qty in ingredients.items():
    scaled_qty = qty * factor
    print(item, ":", scaled_qty, "grams")

pasta : 1000 grams
tomatoes : 800 grams
garlic : 60 grams

迭代字典（dictionary）

# Loop through keys only
for item in ingredients.keys():
    print(item)

pasta
tomatoes
garlic

# Loop through values only
for qty in ingredients.values():
    print(qty, "grams")

500 grams
400 grams
30 grams

range

range(start, end + 1)

start = 起始數字
end = 結束數字
用於產生或調整數值

for i in range(1, 6):
    print(i)

一起來練習吧！

Python 入門（開發者向）