Python知识点梳理

方法和函数区分

fun及Foo.display为函数，obj.display为方法，类实例化后，之前的函数就变成了方法

def fun():
    pass
print(fun)

class Foo(object):
    def display(self):
        pass

print(Foo.display)

obj = Foo()
print(obj.display)

<function fun at 0x0000028F1303D268>
<function Foo.display at 0x0000028F160B48C8>
<bound method Foo.display of <__main__.Foo object at 0x0000028F133ABAC8>>

写一个函数来区分对象

from types import MethodType,FunctionType

def check(args):
    if isinstance(args,MethodType):
        print('这是方法')

    elif isinstance(args,FunctionType):
        print('这是函数')

    else:
        print('这是啥')
check(fun)
check(obj.display)

这是函数
这是方法

小练习

class RoleConfig(object):
    def f1(self,args):
        print('f1',args)

    def f2(self,args):
        print('f2',args)

    def f3(self,args):
        print('f3',args)

    list_display = [f1,f2]

    def get_list_display(self):
        self.list_display.insert(0,obj.f3)
        return self.list_display


obj = RoleConfig()
for item in obj.get_list_display():
    item(obj,2)

报错是因为obj中此时的f3为方法，而f1、f2为函数

Traceback (most recent call last):
  File "D:/Practise/project01/app02/test/20220110.py", line 21, in <module>
    item(obj,2)
TypeError: f3() takes 2 positional arguments but 3 were given

单例模式

编辑三个模块

test1

class AdminSite(object):
    pass

obj1 = AdminSite()

test2

import test1

print(test1.obj1)

import test3

test3

import test1
print(test1.obj1)

执行test2，显示内存地址相同，程序没有重复执行，是直接调用

<test1.AdminSite object at 0x000002CD41700FD0>
<test1.AdminSite object at 0x000002CD41700FD0>

想要使用单例模式，就像test1那样，直接在模块中实例化，其他模块使用时直接调用即可。

静态方法(类变量)

class RoleConfig(object):
    def f1(self,args):
        print('f1',args)

    def f2(self,args):
        print('f2',args)

    def f3(self,args):
        print('f3',args)

    list_display = [f1,f2]

    def get_list_display(self):
        self.list_display.insert(0,RoleConfig.f3)
        return self.list_display


obj = RoleConfig()
for item in obj.get_list_display():
    item(obj,2)
obj1 = RoleConfig()
for item in obj1.get_list_display():
    item(obj1,2)

打印结果为7行数据，第一次执行get_list_display()，list_display列表更新为[f1,f2,f3]

f3 2
f1 2
f2 2
f3 2
f3 2
f1 2
f2 2

解决办法

class RoleConfig(object):
    def f1(self,args):
        print('f1',args)

    def f2(self,args):
        print('f2',args)

    def f3(self,args):
        print('f3',args)

    list_display = [f1,f2]

    def get_list_display(self):
        v = []
        v.extend(self.list_display)  #不要用v=list_display，否则效果跟之前一样
        v.insert(0,RoleConfig.f3)
        return v


obj = RoleConfig()
for item in obj.get_list_display():
    item(obj,2)
obj1 = RoleConfig()
for item in obj1.get_list_display():
    item(obj1,6)

这次就是六个结果了

f3 2
f1 2
f2 2
f3 6
f1 6
f2 6

Python三大器

生成器

迭代器

通过yield可以降低内存消耗

def func(request):
  result = []
  data_list = models.Users.objects.all()
  for row in data_list:
    temp = "%s%s" (row.name,row.pwd,)
    result.append(temp)
  return render(request,'xxx.html',{'result':result})

通过yield优化

def get_result(data_list):
    for row in data_list:
        temp = "%s%s" (row.name,row.pwd)
        yield temp

def func(request):
    data_list = models.Users.objects.all()
    return = get_result(data_list)
    return render(request,'xxx.html',{'result':result})


xxx.html

{% for row in result %}
{{row}}
{% endfor %}

可迭代对象

class Row(object):
  def __init__(self,data):
    self.data = data

  def __iter__(self):
    yield "<div>"
    yield '全部'
    for item in self.data:
      yield "<a href='/index/?p1=1.0'>%s</a>" %item
    yield "</div>"
data_list = [
  Row(['1.0以下','1.1-1.6']),
  Row(['汽油','柴油','混合动力','电动']),
]

for row in data_list:
  for field in row:
    print(field)

封装

##################################老封装思想，后期没有修改变更可以使用
list_filter = [
  {'text':'董方方','gender':'男','color':'xx'},
  {'text':'黄晓雪','gender':'男','color':'xx'},
  {'text':'李贝贝','gender':'男','color':'xx'},
]
for item in list_filter:
  print(item['text']+item['gender'])


###################################新封装思想，后期如果还有变化，可以使用这个方法，两种方式按需采用
class Option(object):
  def __init__(self,text,gender,color):
    self.text = text
    self.gender = gender
    self.color = color
  def get_t_g(self):
    return self.text+self.gender

list_filter = [
  Option(text='董方方',gender='男',color='xx'),
  Option(text='黄晓雪',gender='男',color='xx'),
  Option(text='李贝贝',gender='男',color='xx'),
]

for item in list_filter:
  print(item.get_t_g())

装饰器

functools

def wrapper(func):
    def inner(*args,**kwargs):
        return func(*args,**kwargs)
    return inner
@wrapper
def f1():
    print('f1')
@wrapper
def f2():
    print('f2')

print(f1.__name__)
print(f2.__name__)

结果

inner
inner

有functools

import functools

def wrapper(func):
    @functools.wraps(func)
    def inner(*args,**kwargs):
        return func(*args,**kwargs)
    return inner
@wrapper
def f1():
    print('f1')
@wrapper
def f2():
    print('f2')

print(f1.__name__)
print(f2.__name__)

结果

f1
f2

闭包

闭包
def f1(a1,a2):
  def inner():
    ret = a1 + a2
    return ret
  return inner
  
n1 = f1('test','test1') #内存 a1='test',a2='test1'
n2 = f1('test1','test2')  #内存 a1='test1',a2='test2'
n3 = f1('test3','test4')  #内存 a1='test3',a2='test4'

n1()

# 帮助开发作者维护一个"私密"空间，用于为以后执行提供数据。

反射

getattr

from django.shortcuts import render
from django.http import HttpResponse
# Create your views here.

def test(request):
    from app01 import models
    header_list = []
    list_display=['id','username','phone']
    for name in list_display:
        header_list.append(models.UserInfo._meta.get_field(name).verbose_name)
    print(header_list)
    user_queryset = models.UserInfo.objects.all()
    for item in user_queryset:
        row = []
        for field in list_display:
            v = getattr(item,field)
            row.append(v)
        print(row)

    return HttpResponse('test')

结果

['ID', '姓名', '手机号']
[1, 'name1', 1234]
[2, 'name2', 1234]
[3, 'name3', 1234]

常用

isinstance

判断对象是否为函数

from types import FunctionType
if isinstance(name_or_func,FunctionType):
    val = name_or_func(self,item,False)
else:
    val = getattr(item, name_or_func)
row.append(val)

Django

mark_safe

返回html到页面

from django.utils.safestring import mark_safe
from .models import Role,Dpet
class RoleConfig(StarkConfig):
    def f1(self,row=None,header=False):
        if header:
            return '选择'
        return mark_safe('<input type="checkbox" name="pk" value="%s" />' %row.pk)
    list_display = [f1, 'id', 'title']

reverse

from django.urls import reverse

    def display_edit(self, row=None, header=False):
        if header:
            return '编辑'
        app_label = self.model_class._meta.app_label
        model_name = self.model_class._meta.model_name
        namespace = self.site.namespace
        name = '%s:%s_%s_change'%(namespace,app_label,model_name)
        url = reverse(name,kwargs={'pk':row.pk})
        return mark_safe('<a href="%s"><i class="fa fa-edit" aria-hidden="true"></i></a>'%url)

ModelForm

def add_view(self, request):
        '''
        所有添加页面，都在此函数处理
        使用ModelForm实现
        :param request:
        :return:
        '''
        class AddModelForm(forms.ModelForm):
            class Meta:
                model = self.model_class
                fields = "__all__"

        if request.method == "GET":
            form = AddModelForm()
            return render(request, 'stark/change.html', {'form': form})
        form = AddModelForm(request.POST)
        if form.is_valid():
            form.save()
            redirect(self.reverse_list_url())
        return render(request, 'stark/change.html', {'form': form})

<h1>添加页面</h1>
<div style="width: 680px;margin:0 auto">
        <form class="change" method="post">
        {% csrf_token %}
            {% for field in form %}
                <div class="form-group">
                    <label>{{ field.label }}</label>
                    {{ field }}
                    {{ field.errors.0 }}
                </div>
            {% endfor %}
            <button type="submit" class="btn btn-default">提交</button>
        </form>
    </div>

获取FK/M2M/O2O对应的表中所有的数据

class UserInfo(models.Model):
  title = models.CharField(verbose_name='标题',max_length=32)

  def __str__(self):
    return self.title

class Depart(models.Model):
  name = models.CharField(verbose_name='部门名称',max_length=32)
  tel = models.CharField(verbose_name='联系电话',max_length=32)
  user = models.ForeignKey(verbose_name='负责人',to='UserInfo',on_delete=models.CASCADE)

  def __str__(self):
    return self.name
######fk_obj.rel.model.objects.all()中rel已不能使用，修改为remote_field
def get_fk_queryset(request):
  from app02 import models
  fk_obj = models.Depart._meta.get_field("user")
  user_info_queryset = fk_obj.remote_field.model.objects.all()
  print(user_info_queryset)
  return HttpResponse('...')

Q对象

models.User.object.filter(name__containsj='李')
models.User.object.filter(name__contains='李',email__contains='李')

构造 or
con = Q()
con.children.append(('name__contains','李'))
con.children.append(('email__contains','李'))
models.User.object.filter(name__contains='李',email__contains='李')

c1 = Q()
c1.connector = 'OR'
c1.children.append(('name__contains','李'))
c1.children.append(('email__contains','李'))

c2 = Q()
c2.connector = 'AND'
c2.children.append(('id__gt',2))
c2.children.append(('age__lte',5))

c3 = Q()
c2.connector = 'AND'

c3.add(c1,'AND')
c3.add(c2,'AND')

(name=li or email=li) AND (id>2 and age<=5)

models.User.object.filter(con)

get_字段_display()

gender_choices = ((1, '男'), (2, '女'))
gender = models.IntegerField(verbose_name='性别', choices=gender_choices)
获取性别的名称而不是序号

get_gender_display()