First, the design mode

1.1 MVC

Model (M) is a statement, not a true data, but the data interface.
View (V) is the interface you see, is the presentation models, in addition to providing an interface to collect user input.
The controller (C) controlling the flow of information between the model and the view. Information from the database, by transmitting the information to view the program logic. Also collected by the view information from the user, the view changes, by modifying the model data.

MTV 1.2 (Django)

M represents a "model", the data access layer contains all data-related functions: relationships between data access, validation data, by conduct, data, data.
T represents a "template", the presentation layer . It includes performance-related decision: how to display something on the page or other document types.
V represents the "View", the business logic layer . Logic includes access model and select the appropriate template: a bridge between models and templates.

Second, calls Django environment in a Python script

import os
if __name__ == '__main__':
    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "untitled15.settings")
    import django
    django.setup()

# 测试代码

Three, Django terminal print SQL statements

# settings中配置
LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'handlers': {
        'console':{
            'level':'DEBUG',
            'class':'logging.StreamHandler',
        },
    },
    'loggers': {
        'django.db.backends': {
            'handlers': ['console'],
            'propagate': True,
            'level':'DEBUG',
        },
    }
}

Four, Django request lifecycle

Fifth, the difference Django2.x version 1.x version

　　django2.x of re_path and 1.x of the same url

path basic rules

Angle brackets ( <>) to capture value from the url.
Capture values may comprise a type converter (converter type), such as using <int:name> capture an integer variable. Ruoguo no reformer, will match any string, including of course / the character.
No need to add a leading slash.

path converter

Django's default converter supports the following five:

str, in addition to the matching path separator ( /non-empty string) outside, which is the default.
int, matching positive integer, including 0.
Slug, matching the string of letters, numbers and bars, the underscore.
uuid, matching formatted uuid, as 075194d3-6885-417e-a8a8-6c931e272f00.
path, matches any non-empty string, comprising a path separator (/) (not?)

Registering Custom converter

　　For some complex or require multiplexing, you can define your own converter. Converter is a class or interface, it requires three points:

regex Class attributes, string type

to_python(self, value) Method, value is the class attribute regex is matched string, returns a specific value of the variable Python, for delivery to the corresponding Django view function.
to_url(self, value) Methods, and to_python contrary, value is the value of a specific variable Python, which returns a string, commonly used reverse url reference.

chestnut:

class FourDigitYearConverter:  
    regex = '[0-9]{4}'  
    def to_python(self, value):  
        return int(value)  
    def to_url(self, value):  
        return '%04d' % value

　　Use register_converter to register to the URL configuration:

from django.urls import register_converter, path  
from . import converters, views  
register_converter(converters.FourDigitYearConverter, 'yyyy')  
urlpatterns = [  
    path('articles/2003/', views.special_case_2003),  
    path('articles/<yyyy:year>/', views.year_archive),  
    ...  
]

Six simple file upload

The front end of a bit of attention

1.method need to specify the POST
2.enctype format needs to be changed formdata

Note that temporarily back end

1. Comment out csrfmiddleware intermediate profile
2. Obtain the file data uploaded by the user post by request.FILES

print(request.FILES)
print(type(request.FILES.get('file_name')))

file_name=request.FILES.get('file_name').name
from django.core.files.uploadedfile import InMemoryUploadedFile
with open(file_name,'wb')as f:
    for i in request.FILES.get('file_name').chunks():
        f.write(i)

Seven, choice

　　Defined in the model table: choice = ((0, 'M'), (1, 'M'), (2, 'Unknown'))

　　In the field uses: gender = models.IntegerField (choices = choice)

　　Layer corresponding to the view taken in the text: gender = author.get_gender_display ()

Django's Supplements