构建工作流

Python for Developers 入门

Jasmin Ludolf

Senior Data Science Content Developer

复杂工作流

遍历数据结构
- for、while
评估多个条件
- if、elif、else、>、>=、<、<=、==、!=
更新变量
- +=
返回输出
- print()

"in" 关键字

in = 检查某值是否在变量/数据结构中

recipe = {"pasta": 500, "tomatoes": 400, 
          "garlic": 15, "basil": 20}


if "pasta" in recipe.keys():
    print(True)
else:
    print(False)

True

比遍历每个键更快

"not" 关键字

not = 检查条件是否不成立
用于验证缺失情况

pantry_items = ["flour", "sugar", "olive oil"]

# Check if "salt" is NOT in our pantry
if "salt" not in pantry_items:
    print(True)
else:
    print(False)

True

"and" 关键字

and = 检查是否同时满足多个条件
当需满足多个要求时使用

pasta_quantity = 600
olive_oil_quantity = 30

# Check if we have enough of BOTH ingredients
if pasta_quantity >= 500 and olive_oil_quantity >= 30:
    print(True)
else:
    print(False)

True

"or" 关键字

or = 检查是否满足任一（或更多）条件
当多种选项均可接受时使用

pasta_quantity = 600
olive_oil_quantity = 30

# Check if we have enough of EITHER ingredient
if pasta_quantity >= 500 or olive_oil_quantity >= 30:
    print(True)
else:
    print(False)

True

变量加减

将关键字与其他技术结合，构建复杂工作流

ingredients_checked = 0
for ingredient in recipe_list:
    # ingredients_checked = ingredients_checked + 1
    ingredients_checked += 1

items_to_buy = 10
for item in shopping_list:
    # items_to_buy = items_to_buy - 1
    items_to_buy -= 1

+= 为变量加值，-= 为其减值
其他更新变量的方法

追加（append）

将符合条件的信息存入列表

# Create empty list to hold results
shopping_list = []


# Loop through recipe ingredients
for ingredient, qty_needed in recipe.items():

    # Check if we need to buy it
    if ingredient not in pantry:

        # Add to shopping list
        shopping_list.append(ingredient)

追加（append）

print(shopping_list)

['tomatoes', 'salt']

Passons à la pratique !

Python for Developers 入门