python學習筆記(4) 裝飾器
import time
def timer(f):
def inner():
start = time.time()
ret = f()
end = time.time()
print(end-start)
return ret
return inner #返回函數地址，沒有括號
@timer
def func():
time.sleep(1)
print‘大家好我是渣渣輝‘
return ‘是兄弟就來砍我‘
ret = func() #此處實際上執行的是inner
print(ret)
#在不修改原函數的情況下添加功能，timer就是一個裝飾器函數
#################################################
裝飾器標準格式
def wrapper(f):
def inner(*args,**kwargs):
ret = f(*args,**kwargs)
return ret
return inner
裝飾器的本質：閉包函數
#################################################
from functools import wraps
def wrapper(func):
@wraps(func)
def inner(*args,**kwargs):
print(‘大家好‘)
ret = func(*args,**kwargs)
print(‘這是你沒玩過的全新版本‘)
return ret
return inner
@wrapper #legend = wrapper(legend)
def legend(a):
print(‘我是%s‘%(a))
return ‘是兄弟就來砍我‘
print(legend.__name__)
print(legend.__doc__)
ret = legend(‘渣渣輝‘)
print(ret)
#演示裝飾器和函數的執行順序
######################################################
為多個函數增加記錄調用功能，先將被調用的函數名稱寫入文件
def log(func):
def inner(*args,**kwargs):
with open(‘log‘,‘a‘,encoding= utf8) as f:
f.write(func.__name__+‘\n‘)
ret = func(*args,**kwargs)
return ret
return inner
@log
def shoplist_add():
print(‘購物車增加一件商品‘)
@log
def shoplist_del():
print(‘購物車刪除一件商品‘)
###################################################
為多個函數增加單次登陸驗證
FLAG = 0
def login(func):
def inner(*args,**kwargs):
global FLAG
if FLAG:
ret = func(*args,**kwargs)
return ret
else:
uername = input(‘請輸入用戶名：‘)
userpwd = input(‘請輸入密碼：‘)
if username == ‘天使萌‘ and userpwd ==‘123‘:
FLAG = 1
ret = func(*args,**kwargs)
return ret
else:
print(‘登陸失敗‘)
return inner
@login
def shoplist_add():
print(‘購物車增加一件商品‘)
@login
def shoplist_del():
print(‘購物車刪除一件商品‘)
shoplist_add()
shoplist_add()
shoplist_del()
shoplist_del()
###############################################
讀取網頁內容並儲存到文件，如果文件有內容則直接從文件讀取
import os
from urllib.request import urlopen
def cache(func):
def inner(*args,**kwargs):
if os.path.filesize(‘web_cache‘):
with open(‘web_cache‘,‘wb‘) as f:
return f.read()
ret = func(*args,**kwargs)
with open(‘web_cache‘,‘wb‘) as f:
f.write(b‘*****‘+ret) #以十六進制寫入
return ret
return inner
@cache
def get(url):
code = urlopen(url).read()
return code
ret = get(‘baidu.com‘)
print(‘ret‘)
python學習筆記(4) 裝飾器