Shulou(Shulou.com)06/01 Report--

Editor to share with you what django knowledge points, I believe that most people do not know much about it, so share this article for your reference, I hope you will learn a lot after reading this article, let's go to know it!

1. View function:

Request object-request:

1. HttpRequest.body: request the original data

2. HttpRequest.path: a string indicating the path component of the request (excluding domain name)

3 、 HttpRequest.method

4 、 HttpRequest.GET

5 、 HttpRequest.POST

6 、 HttpRequest.FILES

7. HttpResquest.user: an object of type AUTH_USER_MODEL

Response object:

Return HttpResponse ("") returns string instance

Return render (request, "template", {"": ""}) returns a string instance

Return rredirect ("/ index/") redirect

II. Template language

First, write the function in the views view function and return a rendered page:

Views:

Def foo (request):

Name= "li"

L = [111, 2222, 3333]

D = {"info": [obj1,obj2...]}

Return render (request, "index.html", locals ())

1. Variable: {{name}}

-query the period character in depth. For example: {{d.info.0.name}}

-filter {{name | date: "Y-m-d"}}

two。 Label:

For cycle

{% for i in 1%}

{{i}}

{% empty%}

There are no conditions to meet

{% endfor%}

If judgment statement

{if name= "li"%}

Yes

{% elif%}

{% endif....%}

3. Template syntax

(1) base.html: {% block con%} {% endblock%} in the master

(2) inherit the master index.html:

{% extends "base.html"%} inheritance

{% block con%}

{% endblock%}

3. Models model of ORM

1. Mapping relationship:

Class name of table name-Python in sql

Fields in sql-Class properties of Python

Records in sql-Class objects for Python

2. Single table operation

Class Article (models.Model):

Nid = models.BigAutoField (primary_key=True)

Title = models.CharField (max_length=50, verbose_name=' article title')

Read_count = models.IntegerField (default=0)

(1) add operation

Views:

Copy the code

# method 1:

The article_obj=models.Article.objects.create (nid=1,title= "yuan", read_count=12) # create method returns the currently created article object

# method 2:

Article_obj=models.Article (nid=1,title= "yuan", read_count=12)

Article_obj.save ()

Delete:

Models.Article.objects.filter (title= "python") .delete () # default cascading deletion

Modify:

Models.Article.objects.filter (title= "python") .update (read_count=F ("read_count") + 10)

Query API:

All (): query all results # QuerySet

Filter (* * kwargs): it contains the object # QuerySet that matches the given filter criteria

Get (* * kwargs): returns an object that matches the given filter criteria, and returns one and only one result

An error is thrown if there is more than one or none of the objects that meet the filter criteria. # model object

Exclude (* * kwargs): it contains objects # QuerySet that do not match the given filter criteria

Values (* field): returns a ValueQuerySet-- and a special QuerySet, and the result is not a series.

The instantiated object of model, but an iterative dictionary sequence # QuerySet

Values_list (* field): very similar to values (), it returns a tuple sequence, and values returns a dictionary sequence # QuerySet

Order_by (* field): sort query results # QuerySet

Reverse (): reverse sort the query results # QuerySet

Distinct (): removes duplicate records from the returned result # QuerySet

Count (): returns the number of objects in the database that match the query (QuerySet). # int

First (): returns the first record # model object

Last (): returns the last record # model object

Exists (): returns True if QuerySet contains data, otherwise returns False

QuerySet supports chained operations:

Models.Article.objects.all (). Filter (). Values (). Distinct (). Count ()

QuerySet data type:

1. Sliced and iterated [obj,....]

2. Lazy query:

Articles_list=models.Article.objects.all ()

Use articles_list, such as if articles_list, to convert the sql statement

3. Caching mechanism

Articles_list=models.Article.objects.all ()

For i in articles_list:

Print (i.title) # hit the database

For i in articles_list:

Print (i.title) # not hit the database

=

For i in models.Article.objects.all ():

Print (i.title) # hit the database

For i in models.Article.objects.all ():

Print (i.title) # hit the database

4. Optimize the query

Articles_list=models.Article.objects.all () .iterator ()

For i in articles_list:

Print (i.title) # hit the database

For i in articles_list:

Print (i.title) # No result

Concatenated table operation:

Table relationships:

Class UserInfo (AbstractUser): # settings: AUTH_USER_MODEL = "blog.UserInfo"

"

User information

"

Nid = models.BigAutoField (primary_key=True)

Nickname = models.CharField (verbose_name=' nickname', max_length=32,null=True)

Telephone = models.CharField (max_length=11, blank=True, null=True, unique=True, verbose_name=' mobile phone number')

Avatar = models.FileField (verbose_name=' avatar', upload_to='avatar', default= "avatar/default.png")

Create_time = models.DateTimeField (verbose_name=' creation time', auto_now_add=True)

Class Blog (models.Model):

"

Site information

"

Nid = models.BigAutoField (primary_key=True)

Title = models.CharField (verbose_name=' personal blog title', max_length=64)

Site = models.CharField (verbose_name=' personal blog suffix', max_length=32, unique=True)

Theme = models.CharField (verbose_name=' blog theme', max_length=32)

User = models.OneToOneField (to='UserInfo', to_field='nid')

Class Category (models.Model):

Nid = models.AutoField (primary_key=True)

Title = models.CharField (verbose_name=' classification title', max_length=32)

Blog = models.ForeignKey (blog to which verbose_name=' belongs', to='Blog', to_field='nid')

Class Article (models.Model):

Nid = models.BigAutoField (primary_key=True)

Title = models.CharField (max_length=50, verbose_name=' article title')

Desc = models.CharField (max_length=255, verbose_name=' article description')

# category field: the category object associated with the Article object

Category = models.ForeignKey (verbose_name=' article type', to='Category', to_field='nid', null=True)

# user field: the user field associated with the Article object

User = models.ForeignKey (user to which verbose_name=' belongs', to='UserInfo', to_field='nid')

Tags = models.ManyToManyField (

To= "Tag"

Through='Article2Tag'

Through_fields= ('article',' tag')

)

Class ArticleDetail (models.Model):

Nid = models.AutoField (primary_key=True)

Content = models.TextField (verbose_name=' article content',)

Article = models.OneToOneField (article of verbose_name='', to='Article', to_field='nid')

Class Article2Tag (models.Model):

Nid = models.AutoField (primary_key=True)

Article = models.ForeignKey (verbose_name=' article', to= "Article", to_field='nid')

Tag = models.ForeignKey (verbose_name=' tag', to= "Tag", to_field='nid')

Class Tag (models.Model):

Nid = models.AutoField (primary_key=True)

Title = models.CharField (verbose_name=' tag name', max_length=32)

Blog = models.ForeignKey (blog to which verbose_name=' belongs', to='Blog', to_field='nid'

Add record operation for associated table:

1. Create an article object:

User_obj=models.UserInfo.objects.get (nid=1)

Category_obj=models.Category.objects.get (nid=2)

# one-to-many relationship binding #

# method 1:

Article_obj=models.Article.objects.create (nid=5,title= "picking up every day", user=user_obj,category=category_obj)

# method 2:

Article_obj=models.Article.objects.create (nid=5,title= "picking up every day", user_id=1,category_id=2)

''

Article:

Nid title user_id category_id

5 Chaohua Xi pick up 1 2

''

# # many-to-many relationship binding #

If does not have a mediation model:

Tags = models.ManyToManyField ("Tag")

''

The third table created by ORM:

Article2tags:

Nid article_id tag_id

1 5 1

2 5 2

''

Example: bind kw1,kw2 tag to article_obj

Tag1=Tag.objects.filter (title=kw1) .first ()

Tag2=Tag.objects.filter (title=kw2) .first ()

Article_obj.tags.add (tag1,tag2) #

Article_obj.tags.add (* [tag1,tag2])

Article_obj.tags.add (1 dint 2)

Article_obj.tags.add (* [1pc2])

Dissolve the relationship:

Article_obj.tags.remove (tag1,tag2)

Article_obj.tags.clear ()

Reset the relationship:

Article_obj.tags.clear ()

Article_obj.tags.add (tag1,tag2)

=

Article_obj.tags.set (tag1,tag2)

If has an intermediary model:

Tags = models.ManyToManyField (

To= "Tag"

Through='Article2Tag'

Through_fields= ('article',' tag')

)

Class Article2Tag (models.Model): # Mediation Model

Nid = models.AutoField (primary_key=True)

Article = models.ForeignKey (verbose_name=' article', to= "Article", to_field='nid')

Tag = models.ForeignKey (verbose_name=' tag', to= "Tag", to_field='nid')

Bind a many-to-many relationship, have an intermediary model, and can no longer use article_obj.tags.add (), remove () and other methods

You can only use the Article2Tag table for instance objects.

Example: bind kw1,kw2 tag to article_obj:

Models.Article2Tag.objects.create (tag_id=1,article_id=5)

Models.Article2Tag.objects.create (tag_id=2,article_id=5)

Copy the code

Join table operation (object-based query):

Copy the code

One-to-many queries:

Example 1: query the classified name of the article whose primary key is 4 (forward query, by field)

Article_obj=models.Article.objects.get (nid=4)

Print (article_obj.category.title)

SELECT * FROM "blog_article" WHERE "blog_article". "nid" = 4; / / category_id=2

SELECT * FROM "blog_category" WHERE "blog_category". "nid" = 2

Example 2: query all articles published by user yuan (reverse query, table name _ set)

Yuan=models.UserInfo.objects.get (username= "yuan")

Book_list=yuan.article_set.all () # QuerySet

Many-to-many queries:

Example 3: query the tag name of an article with a primary key of 4 (forward query, by field)

Article_obj=models.Article.objects.get (nid=4)

Tag_list=article_obj.tags.all () # finds the associated tag record in the tag table through Article2Tag

For i in tag_list:

Print (i.title)

Example 4: query all articles corresponding to this tag developed by web (reverse query, by table name _ set)

Tag_obj=models.Tag.objects.get (title= "web Development")

Article_list=tag_obj.article_set.all ()

For i in article_list:

Print (i.title)

Example 5: query the author names of all articles corresponding to this tag developed by web

Tag_obj=models.Tag.objects.get (title= "web Development")

Article_list=tag_obj.article_set.all ()

For article in article_list:

Print (article.user.username)

Cross-table query based on QuerySet (forward query, by field; reverse query, by table name)

One-to-many queries:

Example 1: query the classification name of an article with a primary key of 4

Models.Article.objects.filter (nid=4) .values ("category__title")

Models.Category.objects.filter (article__nid=4) .values ("title")

Example 2: query all articles published by user yuan

Models.UserInfo.objects.filter (username= "yuan") .values (article__title)

Models.Article.objects.filter (user__username= "yuan") .values ("title")

Many-to-many queries:

Example 3: query the tag name of an article with a primary key of 4 (forward query, by field)

Models.Article.objects.filter (nid=4) .values ("tags__title")

Models.Tag.objects.filter (article__nid=4) .values ("title")

Example 4: query all articles corresponding to this tag developed by web (reverse query, by table name _ set)

Models.Article.objects.filter (tags__title= "web development"). Values ("title")

Models.Tag.objects.filter (title= "web development"). Values ("article__title")

Example 5: query the author names of all articles corresponding to this tag developed by web

Models.Tag.objects.filter (title= "web development"). Values ("article__user__username")

Models.UserInfo.objects.filter (article__tags__title= "web development"). Values ("username")

The above is all the contents of the article "what are the knowledge points of django". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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