decorator, viewsystem 063
The long-awaited decorator is finally here!!!
1 decorator
Definition: Without changing the calling method of the original function and adding additional functions to the function
Create a new python file and write in it
Introduction: Define a function to print the execution time when the function is called and executed (introduce the event module)
You can define a time function and pass the function that needs to be executed into the time function. That's it.
Problem: This changes the way the function is called
import time def timer(func): def inner(): print (time.time()) ret = func() #Original function return ret return inner def func1(): print (func1) return ' the return value of func1 ' a = timer(func1) #The return value at this time is the return value of inner a() #The calling method is still changed # Use the func1 below = timer(func1) func1() #The calling method will not change in this way # Decorator It is an application of closure
# It can also be used in this way, this is the case of using syntax to use decorators
@timer # Equivalent to func1 = timer(func1)
def func1():
print(func1)
return 'the return value of func1'
func1()
Closures are used
example code
#Definition dating function # You need to download the software first def download(func): # Add function to the function def inner(): print ( ' download software ' ) func() return inner #Use different tools about # def yue(tools): # print('Use {} to make an appointment'.format(tools)) # yue = download(yue) @download def yue(tools): print ( ' Use {} to make an appointment ' .format(tools)) #Original function Carry the parameter yue( ' momo ' ) #now it is the inner in the decorator yue( ' tantan ' ) yue( ' Drifting bottle ' )
How to write a complete decorator
#standard writing def wrapper(func): def inner(*args,** kwargs): #execute the operation before the decorated function ret = func(*args,** kwargs) #execute the operation after the decorated function return ret return inner #decorate the function @wrapper def func1(): print ( ' func1 ' ) func1()
Advanced content of decorators:
#Control multiple decorators # Define a switch # Globally define one # flag = True # if #judgment flag import time flag = True def outer(flag): def timer(func): def inner(*args,** kwargs) if flag: print (time.time()) ret = func(*args,** kwargs) else : ret = func(*args,** kwargs) return ret return inner @outer(True) def func1(): print ( ' func1 ' ) will execute the decorator @outer(False) def func2(): print ( ' func2 ' ) func1() func2()
After printing the results, we will find that the func2 function does not print the time, that is, the effect of writing a decorator but not adding a device to func2 is realized.
Multiple decorators decorate the same function:
# Fixed usage def wrapper1(func1): def inner(*args,** kwargs): print ( ' before wrapper1 ' ) #2 ret = func(*args,** kwargs) print ( ' after wrapper1 ' ) #5 return ret return inner def wrapper2(func2): def inner(*args,** kwargs) print ( ' before wrapper2 ' ) #1 ret = func(*args,** kwargs) print( ' after wrapper2 ' ) #4 return ret return inner @wrapper2 # func1 = wrapper2(func1) wrapper2.inner @wrapper1 # func1 = wrapper1(func1) wrapper1.inner
#func = func1 def func1(): print ( ' func1 ' ) #3 return ' the return value of func1 ' print( func1()) # 6
# The way of thinking in this way is firstly wrapper1 decorates func1 first, after the decoration, func1 = wrapper(func1), that is,
#func1 at this time is actually of wrapper1 Decorating the inner function is also about decorating the inner function of wrapper1
#that is, func1 = the inner function of wrapper1, so the final display result is to execute the inner function of wrapper2 first and print 'before wrapper2'
#Continue to execute, the function at this time is the inner function of wrapper1, which jumps to wrapper1, prints 'before wrapper1', and then executes
# is the wrapped function in wrapper1, that is, the real func1 prints 'func1' Then go down and print 'after wrapper1' and then return d to
'after wrapper2' After executing the decorator, it will execute its own return value
# After execution, return to itself and then continue
You can use this picture to understand the decoration and display it in order. After each layer is executed, it will return to itself and continue downward.
Decorator Repair Techniques:
#Need to know which function is executed # print(func1(__name__)) # from functools import wraps #Put @wraps(func) on the inner to import time from functiontools import wraps def timer(func): @wraps (func) def inner(): print (time.time()) ret = func() #Original function return ret return inner @timer # func1 = timer(func1) def func1(): """ func1 xxxx :return : """ print ( ' func1 ' ) return ' return value of func1 ' @timer # func1 = timer(func1) def func2(): """ func2 xxxx :return: """ print ( ' func2 ' ) return ' return value of func2 ' print (func1. __name__ ) print (func2. __name__ ) print (func2.__doc__ ) #Adding this line will display the comment of function 2. Adding this item in the log can identify which function is executed and the display result is func1 func2 func2 xxxx :return:
2 view system
1 CBV and FBV
FBV(function based view)
CBV(class based view)
What we have written before are function-based views, called FBV. Views can also be written as class-based.
Steps to write CBV:
1 Definition:
#Add Publisher CBV from django.views import View class AddPublisher(View): def get(self, request): pass def post(self, request): pass
2 uses:
url(r ' ^add_publishe/ ' , views.AddPublisher.as_view()) # Must have brackets to execute
3 CBV process:
1:
views.AddPublisher.as_view() Execute the view function when the program is loaded
2: Execute the view function when the request comes: 1 self = AddPublisher() 2 self.request = request 3: Execute the self.dispatch method: 1 When judging whether the request method is allowed, obtain the get or defined in AddPublisher through reflection When the post method is not allowed through the handler, self.http_method_not_allowed also gets 2 through the handler. Execute the handler to get the return result HttpResponse object
4. Add a decorator to CBV
from django.utils.decorators import method_decorator
1 Load a get/post method:
@method_decorator(timer) def get(self,request): # 2 Load the self.dispatch method (recommended usage) @method_decorator(timer) def dispatch(self,request,*args,** kwargs); # 3Add to the class On @method_decorator(timer,name= ' post ' ) #There must be a name field to specify which way to add a decorator @method_decorator(timer,name= ' get ' ) class AddPublisher(view):
A simple example is as follows
class AddPublisher(View): #You can define the method of request yourself # http_method_names = ['get'] @method_decorator(timer) def dispatch(self, request, *args, ** kwargs): # Operation # start = time.time( ) ret = super(). dispatch (request, *args, ** kwargs) # end = time.time() # print('time: {}'.format(end - start)) #operation return ret # @method_decorator (timer) def get(self, request): print ( ' get ' ) return render(request, 'add_publisher.html') # @method_decorator(timer) def post(self, request): print('post') err_msg = '' new_name = request.POST.get('new_name') if not new_name: err_msg = '不能为空' obj_list = models.Publisher.objects.filter(name=new_name) if obj_list: err_msg = '数据已存在' if new_name and not obj_list: ret = models.Publisher.objects.create(name=new_name) return redirect('/publisher_list/') return render(request, 'add_publisher.html', { 'err_msg': err_msg, 'new_name': new_name})
2 request
request.method #Judge the request method request.GET #Get information on the url Similar to a dictionary, you can get it through get() or [] request.POST #Get the POST data submitted on the form request.body #Request body request. The data of POST is the request.FILES obtained from the body #A dictionary-like object contains all uploaded file information # Notes # 1. Enctype needs to be added to the form enctype = ' multipart/form-data ' # 2. Add the method Change to post Add name attribute Add {% csrf_token %} method = ' post ' name= '' {% csrf_token % } # 3. Pay attention to the method of setting the file object chunks # 上传文件 def upload(request): if request.method =='POST': file = request.FILES.get('f1') with open(file.name, 'wb') as f: for chunk in file.chunks(): f.write(chunk) return HttpResponse('上传成功') return render(request,'upload.html') # html页面 <form action="" method="post" enctype="multipart/form-data"> { % csrf_token %} 文件：<input type="file" name="f1"> <button>上传</button> </form>
JsonResponse
JsonResponse is a subclass of HttpResponse designed to generate JSON-encoded responses
from django.http import JsonResponse def json_test(request): data = { ' name ' : ' dsb ' , ' age ' : ' 12 ' } return JsonResponse(data) #The second method manually sets the return value def json_test(request ): data = { ' name ' : ' dsb ' , ' age ' : ' 25 ' } return HttpResponse(json.dumps(data),Content-Type='application/json')