switcher ={

   :'sunday',

   :'monday',

   :'thuesday'

}

day =

day_name=switcher.get(day,'Unknow')

print(day_name)  # sunday

def get_sunday():

    return 'sunday'

def get_monday():

    return 'monday'

def get_thuesday():

    return 'thuesday'

def get_default():

    return 'Unknow'

switcher ={

   :get_sunday,

   :get_monday,

   :get_thuesday

}

day =

day_name=switcher.get(day,get_default)()

print(day_name)  # sunday

# 列表推到式

# 集合推到式

# map filter

# set

# dict

a = [,,,,,,,]

# b = [i*i for i in a]

b = [i** for i in a]

print(b)  # [, , , , , , , ]

c = [i** for i in a]

print(c)  # [, , , , , , , ]

d = [i** for i in a if i > ]

print(d)  # [, , ]

e =(,,,,,,,)

f = [i** for i in a if i > ]

print(f)  # [, , ]

g = {i** for i in a if i > }

print(g)  # {, , }

students = {

    '喜小乐':,

    '石敢当':,

    '张三':

}

# 字典

b = {key for key,value in students.items()}

print(b)  # {'石敢当', '喜小乐', '张三'}

b = {value for key,value in students.items()}

print(b)  # {, , }

b = {value:key for key,value in students.items()}

print(b)  # {: '喜小乐', : '石敢当', : '张三'}

# 元组

b = (key for key,value in students.items())

for x in b:

    print(x)

# 喜小乐

# 石敢当

# 张三

# None 空

# 空字符串 空的列表  False

a = ''

b = False

c =[]

print(a==None)      # False

print(b==None)      # False

print(c==None)      # False

print(a is None)    # False

print(type(None))   # <class 'NoneType'>

a = []

a =''

a = None   # 不存在

a = False  # 真假

判断为空的方式

if a:

if not a:

class Test():

    def __len__(self):

        return

        # return

        # return True

test = Test()

if test:

    print('S')  # True/

else:

    print('F')  # 

print(len(Test()))   #

print(bool(Test()))  # False

class Test():

    def __bool__(self):

        return False

    def __len__(self):

        return True

test = Test()

if test:

    print('S')

else:

    print('F')  # F