python从入门到实践之第4章 操作列表

遍历整个列表

使用for循环

 magicians = ['alice', 'david', 'carolina']  
 for magician in magicians: #这行代码让Python从列表magicians 中取出一个名字，并将其存储在变量magician中
    print(magician) #需要缩进才能循环

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")
print("Thank you, everyone. That was a great magic show!") #不缩进就不在循环内

小心错误：缩进错误、for语句后忘了冒号

创建数值表列

使用range

for value in range(1,5):
    print(value)

注意，输出的是1到4，不包含最后一个

创建数字列表

numbers = list(range(1,6))
print(numbers)

输出[1, 2, 3, 4, 5]

指定步长：

even_numbers = list(range(2,11,2))
print(even_numbers)

输出[2,4,6,8,10]

创建一个平方数列表

 squares = []  
 for value in range(1,11): 
     square = value**2    
     squares.append(square)
     print(squares)

输出[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

还可以简化代码

squares = []
for value in range(1,11)
    squares.append(value**2)
    
print(squares)

列表解析（进一步简化）

squares = [value**2 for value in range(1,11)]
print(squares)

使用列表的一部分

切片

只打印第1到3名运动员如下：

players = ['charles', 'martina', 'michael', 'florence', 'eli']  
print(players[0:3])

自动从头开始如下：

print(players[:4])

遍历切片

打印前三个

 for player in players[:3]:
     print(player.title())

复制列表：同时省略起始索引和终止索引

 my_foods = ['pizza', 'falafel', 'carrot cake']  
 friendfoods = myfoods[:]

如果用

 friendfoods = myfoods

会导致当myfoods添加或删除时，friendfoods也一起变化

元组

使用圆括号，注意元组元素不能变，除非重新定义整个元组

 dimensions = (200, 50)

PEP 8
每级用四个空格缩进
每行不超过80个字符
用空格把不同部分隔开