1. 条件控制
- # if-elif-else 结构
- age = 12
- if age <4:
- price = 0
- elif age < 18:
- price = 5
- else:
- price = 10
- print("Your admission cost is $" + str(price) + ".")
- # Your admission cost is $5.
可以使用多个 elif 代码块, 也可以省略 else 代码块.
1.1 使用 if 语句处理列表
- # 确定列表不是空的
- requested_toppings = []
- if requested_toppings:
- for requested_topping in requested_toppings:
- print("Adding" + requested_topping + ".")
- print("\nFinished making your pizza!")
- else:
- print("Are you sure you want to plain pizza?")
- # Are you sure you want to plain pizza?
- # 使用多个列表
- available_toppings = ['mushrooms', 'olives', 'green peppers', 'pepperoni', 'pineapple', 'extra cheese']
- requested_toppings = ['mushrooms', 'french fries', 'extra cheese']
- for requested_topping in requested_toppings:
- if requested_topping in available_toppings:
- print("Adding" + requested_topping + ".")
- else:
- print("Sorry, we don't have "+ requested_topping +".")
- print("\nFinished making your pizza!")
- # Adding mushrooms.
- # Sorry, we don't have french fries.
- # Adding extra cheese.
- #
- # Finished making your pizza!
2. 循环语句
- n = 100
- sum = 0
- counter = 1
- while counter <= n:
- sum = sum + counter
- counter += 1
- print("1 到 %d 之和为: %d" % (n,sum))
- # 1 到 100 之和为: 5050
2.1 while 循环使用 else 语句
- count = 0
- while count < 5:
- print (count, "小于 5")
- count = count + 1
- else:
- print (count, "大于或等于 5")
- # 0 小于 5
- # 1 小于 5
- # 2 小于 5
- # 3 小于 5
- # 4 小于 5
- # 5 大于或等于 5
如果你的 while 循环体中只有一条语句, 你可以将该语句与 while 写在同一行中.
while(True): print('Hello!')
注意: 以上的无限循环你可以使用 CTRL+C 来中断循环.
2.2 for 语句
- languages = ["C", "C++", "Perl", "Python"]
- for x in languages:
- print (x)
- # C
- # C++
- # Perl
- # Python
2.3 break 语句
- n = 1
- while n <= 10:
- if n> 5: # 当 n = 6 时, 条件满足, 执行 break 语句
- break # break 语句会结束当前循环
- print(n)
- n = n + 1
- print('END')
- # 1
- # 2
- # 3
- # 4
- # 5
- # END
2.4 continue 语句
- n = 0
- while n < 10:
- n = n + 1
- if n % 2 == 0: # 如果 n 是偶数, 执行 continue 语句
- continue # continue 语句会直接继续下一轮循环, 后续的 print() 语句不会执行
- print(n)
- # 1
- # 3
- # 5
- # 7
- # 9
参考资料:
Python3 教程 | 菜鸟教程
Python 教程 - 廖雪峰的官方网站
《Python 编程从入门到实践》--[美] Eric Matthes 著
来源: http://www.bubuko.com/infodetail-3013021.html