Python 遍历整个列表

操作列表

• 遍历整个列表，无论列表有多长，循环让列表中的每一个元素都采取一个或一系列相同的措施，从而高效地处理任何长度的列表，包含数以千至数百万个元素的列表。

遍历整个列表

• 通过for循环解决遍历
• 从列表中取出一个元素放入新的变量中，最后打印新的变量，最后重复执行这两步

# 遍历整个列表案例
magicians = ['alice','david','carolina']
# 从列表中取出一个元素放入新的变量中，最后打印新的变量
for magician in magicians:
    print(magician)

alice
david
carolina

深入地研究循环

• 循环是计算机自动完成重复工作的常见方式之一。
• 对列表中的每个元素，都将执行循环指定的步骤，而不管列表包含多少个元素。如果列表包含一百万个元素， Python 就重复执行指定的步骤一百万次，且通常速度非常快。
• 编写 for 循环时，对于用于存储列表中每个值的临时变量，可指定任何名称。然而，选择描述单个列表元素的有意义的名称大有帮助。

# 临时变量名称案例
for cat in cats:
for dog in dogs:
for item in list_of_items:

在for循环中执行更多的操作

• for循环中，可以对每个元素执行任何操作

# for循环执行操作案例
magicians = ['alice','david','carolina']
for magician in magicians:
    print(magician.title() + ",that was a great trick!")
    print("I can't wait to see your next trick, " + magician.title() + ".\n")

Alice,that was a great trick!
I can't wait to see your next trick, Alice.

David,that was a great trick!
I can't wait to see your next trick, David.

Carolina,that was a great trick!
I can't wait to see your next trick, Carolina.

在for循环结束后执行一些操作

• 在 for 循环后面，没有缩进的代码都只执行一次，而不会重复执行。

# for循环结束后执行案例
magicians = ['alice','david','carlolina']
for magician in magicians:
    print(magician.title() + ", that was a great trick!")
    print("I can't wait to see you next trick, " + magician.title() + ".\n")

print("Thank you, enveryone. That was a great magic show!")

Alice, that was a great trick!
I can't wait to see you next trick, Alice.

David, that was a great trick!
I can't wait to see you next trick, David.

Carlolina, that was a great trick!
I can't wait to see you next trick, Carlolina.

Thank you, enveryone. That was a great magic show!

练习

# 1.比萨
# 想出至少三种喜欢的比萨，将其名称存储在一个列表中，再使用for循环将每种比萨的名称都打印出来
# 修改这个for循环，使其打印包含比萨名称的句子，对于每种比萨都显示一行输出，如“I like pizza”
# 在程序末尾添加一行代码，不在for循环里，指出你有多喜欢比萨，输出应包含对每种比萨的消息，还有一个总结性句子，如“I reall love pizza”
pizzas = ['chess pizza','beef pizza','corn pizza','pepperoni pizza']
for pizza in pizzas:
    print(pizza)
print("#" * 20)
for pizza in pizzas:
    print("I like " + pizza.title() + "!")
print("\nI reall love pizza！")

chess pizza
beef pizza
corn pizza
pepperoni pizza
####################
I like Chess Pizza!
I like Beef Pizza!
I like Corn Pizza!
I like Pepperoni Pizza!

I reall love pizza！

# 2.动物
# 想出至少3种有共同特征的动物，将这些动物的名称存储在一个列表中，再使用for循环将每种动物的名称都打印出来
# 修改这个程序，使每种动物都打印一个句子，如“A dog would make a great pet”。
# 在程序末尾添加一行代码，指出这些动物的共同之处，如：“Any of these animals would make a great pet!”
animals = ['goat','sheep','lamb']
for animal in animals:
    print(animal)
    print("A " + animal.title() + " would make a great pet.")
print("\nAny of these animals would make a great pet!")

goat
A Goat would make a great pet.
sheep
A Sheep would make a great pet.
lamb
A Lamb would make a great pet.

Any of these animals would make a great pet!