python3基础之pythonic

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

五、git地址

https://coding.net/u/RuoYun/p/Python-Programming-Notes/git/tree/master/0.basics/12.pythonic