一、字典代替switch
In [13]:
def get_sunday():
return 'Sunday'
def get_default():
return 'nothing'
switcher = {0:get_sunday} # 建立字典
day = 0
day_name = switcher.get(day,get_default)()
print(day_name)
day = 1
day_name = switcher.get(day,get_default)()
print(day_name)
Sunday
nothing
二、列表推导式
概念:已存在列表推倒新列表
In [14]:
a = [1,2,3]
b = [i*i for i in a]
print(b)
[1, 4, 9]
In [15]:
### 增加筛选功能
In [16]:
c = [i*i for i in a if i>=2]
print(c)
[4, 9]
三、用字典编写列表推导式
In [17]:
students = { '学生1':10, '学生2':12}
d = {key for key,value in students.items()}
print(d)
{'学生1', '学生2'}
四、None类型
概念: None 空。不等于空字符串,列表,false
In [18]:
print(type(None))
a = ''
b = False
c = []
print(a == None)
print(b == None)
print(c == None)
<class 'NoneType'>
False
False
False
In [19]:
def fun1():
pass
# 判空操作
if a:
print(True)
else:
print(False)
False