python基础知识内置函数（二）、装饰器

r= chr(65)        #ASCII对应的字母
print (r)      

n= ord("a")      #ASCII对应的数字
print(n)

#以下为执行结果
A
97

import random

li=[]
for  i in range(6):
    r = random.randrange(0,5)
    if  r ==2 or  r==4:
        num = random.randrange(0,10)
        li.append(str(num))
    else:
        temp = random.randrange(65,91)
        c = chr(temp)
        li.append(c)
result ="".join(li)
print (result)

#以下为执行多次的结果
DR2B5G

59BY9F

6EQ8ZP

s = "print (123)"
#将字符串编译成python代码
r =compile(s,"<string>","exec")
#执行python代码 没有返回值
exec(r)

s = "8*8"
#只能执行表达式  有返回值
ret = eval(s)
print (ret)

#以下为执行行结果
123
64

print (dir(list))#快速查看 对象提供了哪些功能呢
#以下为执行结果：  [‘__add__‘, ‘__class__‘, ‘__contains__‘, ‘__delattr__‘, ‘__delitem__‘, ‘__dir__‘, ‘__doc__‘, ‘__eq__‘, ‘__format__‘, ‘__ge__‘, ‘__getattribute__‘, ‘__getitem__‘, ‘__gt__‘, ‘__hash__‘, ‘__iadd__‘, ‘__imul__‘, ‘__init__‘, ‘__iter__‘, ‘__le__‘, ‘__len__‘, ‘__lt__‘, ‘__mul__‘, ‘__ne__‘, ‘__new__‘, ‘__reduce__‘, ‘__reduce_ex__‘, ‘__repr__‘, ‘__reversed__‘, ‘__rmul__‘, ‘__setattr__‘, ‘__setitem__‘, ‘__sizeof__‘, ‘__str__‘, ‘__subclasshook__‘, ‘append‘, ‘clear‘, ‘copy‘, ‘count‘, ‘extend‘, ‘index‘, ‘insert‘, ‘pop‘, ‘remove‘, ‘reverse‘, ‘sort‘]

r =divmod(97,10)  #除法余数

print (r) 

#以下为执行结果： 
(9, 7)

s = "alex"
r = isinstance(s,str)  #用于判断对象是否是类的实例
print(r)

#以下为执行结果: 
True

#filter (函数,可迭代的对象)
def f2(a):
    if a>22:
        return  True
li = [11,22,33,44,55]

ret = filter(f2,li)   #filer,迭代第二参数，让每个元素执行函数，函数返回值为True，表示元素合法
print (list(ret))

#以下为执行结果
[33, 44, 55]

li = [11,22,33,44,55]
result = filter(lambda a:a>33,li)
print  (list(result))

#以下为执行结果
[44, 55]

#map(函数,可迭代的对象)

def f2(a):
       return  a+ 100
li = [11,22,33,44,55]
result = map(f2,li)
print (list(result))

#以下为执行结果：
[111, 122, 133, 144, 155]

li = [11,22,33,44,55]
result = map(lambda a:a+100,li)
print (list(result))

#以下为执行结果：
[111, 122, 133, 144, 155]

NAME ="ALEX"
def show():
    a = 123
    c = 123
    print (locals())  #局域变量
    print(globals())  #全局变量
show()

#以下为执行结果
{‘c‘: 123, ‘a‘: 123}
{‘__doc__‘: None, ‘__package__‘: None, ‘__cached__‘: None, ‘__name__‘: ‘__main__‘, ‘__loader__‘: <_frozen_importlib_external.SourceFileLoader object at 0x7f04b77e8da0>, ‘__spec__‘: None, ‘NAME‘: ‘ALEX‘, ‘__builtins__‘: <module ‘builtins‘ (built-in)>, ‘show‘: <function show at 0x7f04b77e6158>, ‘__file__‘: ‘a.py‘}

s = "hahah"
print  (hash(s)) #哈希值

#以下为执行结果：
-8346297972582505313

# python3  len判断是字符个数  python2是字节个数
s = "李杰"
print(len(s))  

#python3查询字节个数可以用 bytes()
s = "李杰"
b = bytes(s,encoding=‘utf-8‘)
print (len(b))

#以下为执行结果
2
6

r = max([1,2,3,4])   #最大值
print (r)

#以下为执行结果：
4

r = min([1,2,3,4])    #最小值
print (r)

#以下为执行结果：
1

r = sum([1,2,3,4])   #求和
print (r)

#以下为执行结果：
10

print  (round(1.4))   #四舍五入

以下为执行结果：
1

li =[11,22,3,4]
print (sorted(li))  #不改变原列表排序
li.sort()                #对原列表进行排序
print (li)

#以下为执行结果：
[3, 4, 11, 22]
[3, 4, 11, 22]

l1=["alex",11,22,33]
l2=["aaa",11,22,33]
l3 =["bbb",11,22,33]
r = zip(l1,l2,l3)  #zip函数接受任意多个（包括0个和1个）序列作为参数，返回一个tuple列表
print (list(r))

#以下为执行结果：
[(‘alex‘, ‘aaa‘, ‘bbb‘), (11, 11, 11), (22, 22, 22), (33, 33, 33)]

l1=["alex",11,22,33]
l2=["aaa",11,22,33]
l3 =["bbb",11,22,33]
r = zip(l1,l2,l3)
#print (list(r))
temp = list(r)[0]
ret = ‘ ‘.join(temp)
print(ret)

#以下为执行结果：
alex aaa bbb

def outer(func):
    def inner():
        print (‘before‘)
        r = func()
        print ("after")
        return r
    return inner()

@outer
def f1():
    print ("F1")
    return  "aaa"
print (f1)

#以下为执行结果：
before
F1
after
aaa

def outer(func):
    def inner(a):
        print (‘before‘)
        r = func(a)
        print ("after")
        return r
    return inner

@outer
def f1(arg):
    print ("F1")
    return  "aaa"
ret = f1("wudalang")
print (ret)

#以下为执行结果：
before
F1
after
aaa

def outer(func):
    def inner(*args,**kwargs):
        print (‘before‘)
        r = func(*args,**kwargs)
        print ("after")
        return r
    return inner

@outer
def f1(arg):
    print("F1")
    return "kaka"

@outer
def f2(arg1,arg2):
    print ("F2")
    return  "aaa"
@outer
def f3():
    print ("F3")

ret = f1("fafafa")

print ("返回值",ret)
ret1 = f2(11,22)

print ("返回值",ret1)

#以下为执行结果：
before
F1
after
返回值 kaka
before
F2
after
返回值 aaa