1. if语句
1.1 if-elif-else结构
>>> age=12
>>> if age < 4:
... price = 0
... elif age < 18:
... price = 5
... else:
... price = 10
...
>>> price
5
1.2 使用if判断列表是否为空
>>> str = []
>>> if str:
... a = 1
... else:
... a = 0
...
>>> a
0
2. 用户输入
2.1 input()的简单使用
-
>>> message = input("please input your name: ")
please input your name: Jack
>>> message
'Jack'
>>> message = "please input something.\nName: "
>>> name = input(message)
please input something.
Name: Jack
>>> name
'Jack'
- 使用函数input()时,python将用户输入解读为字符串。可使用函数int(),将数字的字符串表示转换为数值表示
-
>>> age = input("How old are you? ")
How old are you? 12
>>> age
'12'
>>> age = int(age)
>>> age
12
3. while语句
3.1 使用while循环处理列表和字典
- for循环可以遍历列表,但在for循环中不应修改列表,否则将导致python难以跟踪其中的元素。要在遍历列表的同时对其进行修改,可使用while循环
-
>>> a = ['alice', 'brian', 'candace']
>>> b = []
>>> while a:
name = a.pop(0)
print(name)
b.append(name)
alice
brian
candace
>>> b
['alice', 'brian', 'candace']
- 利用while和remove()函数来删除列表中所有包含特定值的元素
-
>>> pets = ['dog', 'cat', 'dog', 'goldfish', 'cat', 'rabbit', 'cat']
>>> while 'cat' in pets:
pets.remove('cat')
>>> pets
['dog', 'dog', 'goldfish', 'rabbit']