概览

web 开发的历史

• 以前web开发，升级的时候需要手动修改 html

• CGI NCSA(NCSA Mosaic 浏览器) –> 使得 web server端 可以自动生成 html

    Common Gateway Interface, or CGI 通用网关协议
      
    CGI的发展推动了 动态网站的发展
      
    缺点： 
          
        CGI脚本需要包含很多的 重复的模板
  

• PHP 的简易设计可以很好的嵌入 HTML

    缺点：
        代码重复， 简单， 冗余， 漏洞
          
        网络安全
  

• Web-development frameworks Django , Rails

关于作者

Malcolm Tredinnick 是 Django 的核心developer (R.I.P) 

Two Scoops of Django 的 审阅者

coding style 代码风格

保持良好的代码习惯，利于阅读和维护

➤ Avoid abbreviating variable names.
   命名变量避免使用缩写
➤ Write out your function argument names.
   写全函数的参数名
➤ Document your classes and methods.
   注释类和方法
➤ Comment your code.
   注释代码
➤ Refactor repeated lines of code into reusable functions or methods.
   用函数和方法代替 重复的代码
➤ Keep functions and methods short. A good rule of thumb is that scrolling should not be necessary to read an entire function or method.
   保持每个函数和方法精简， (不要用鼠标拖动 :) )

balance_sheet_decrease 比 缩写的bsd or bal_s_d要更容易理解， 记忆

PEP 8

PEP 8is the official style guide for Python。python.org/dev/peps/pep-0008/

一些PEP 8的建议 :

➤ “Use 4 spaces per indentation level.”
   缩进使用4个空格
   
➤ “Separate top-level function and class definitions with two blank lines.”
   函数或者类之间间隔要用两个空行
   
➤ “Method definitions inside a class are separated by a single blank line.”
   类方法之间的间隔使用一个空行

可以使用一些IDE auto-pep8插件工具 Flake8，自动调节

保持已有项目的风格

当然如果已有的项目中代码风格不是`PEP8`， 需要遵从已有项目的风格

The 79-Character Limit

➤ On open source projects, there should be a hard 79-character limit. Our experience has shown
that contributors or visitors to these projects will grumble about line length issues; however, it
has not kept contributors away and we feel the value isn’t lost.
开源项目使用 79 limit

➤ On private projects, we relax the limit to 99 characters, taking full advantage of modern monitors.
个人项目使用 99 limit

import顺序

1 Standard library imports
2 Related third-party imports
3 Local application or library specific imports

# Stdlib imports
from math import sqrt
from os.path import abspath

# Core Django imports
from django.db import models
from django.utils.translation import ugettext_lazy as _

# Third-party app imports
from django_extensions.db.models import TimeStampedModel

# Imports from your apps
from splits.models import BananaSplit

使用相对引用

# cones/views.py
from django.views.generic import CreateView

# Relative imports of the 'cones' package
from .models import WaffleCone
from .forms import WaffleConeForm
from core.views import FoodMixin

class WaffleConeCreateView(FoodMixin, CreateView):
    model = WaffleCone
    form_class = WaffleConeForm

Absolute vs. Explicit Relative vs. Implicit Relative

Code	Import Type	Usage
from core.views import FoodMixin	absolute import	Use when importing from outside thecurrent app
from .models import WaffleCone	explicit relative	Use when importing from another module in the current app
from models import WaffleCone	implicit relative	Often used when importing from another module in the current app, but not a good idea

避免使用 import *

避免命名冲突

# 相同的变量名
from django.db.models import CharField
from django.forms import CharField

# rename
from django.db.models import CharField as ModelCharField
from django.forms import CharField as FormCharField