开发者学堂课程【Python入门 2020年版：读取文件并返回给浏览器】学习笔记，与课程紧密联系，让用户快速学习知识。
课程地址：https://developer.aliyun.com/learning/course/639/detail/10484
读取文件并返回给浏览器
1.代码：
from wsgiref.simple_server import make_server
def demo_app(environ,start_response):
path=environ[‘PATH_INFO’]
status_code=’200 OK’
if path == '/':
response =’欢迎来到我的首页'
elif path =='/test':
response = '欢迎来到test页面'
elif path == ‘/demo' :
response = '欢迎来到demo页面'
else:
status_code=’404 Not Found’
response = '页面走丢了’
start_response(‘status_code’,[(‘Content-Type,’text/html;charset=utf8’)])
return [‘response’.encode(‘utf8’)]
if_ name_=='_ main_ ':
httpd : make_server(‘’, 8080, demo_app):
sa = httpd.socket. getsockname()
print("Serving HTTP on", sa[0], "port", sa[1], "...")
httpd.serve_forever()
2.如何返回不同的内容
现在返回的都是字符串，那么能不能返回不同的内容呢?
把字典改成json字符串返回,再读取并返回一个文件，文件xxxx.txt先建好，里面输入：我是文件里的内容。
（1）json字符串返回
修改代码：
from wsgiref.simple_server import make_server
def demo_app(environ,start_response):
path=environ[‘PATH_INFO’]
status_code=’200 OK’
if path == '/':
response =’欢迎来到我的首页'
elif path =='/test':
response = json.dumps({‘name’:’zhangsan’,’age’:18})
elif path == ‘/demo' :
with open(‘page/xxxx.txt’,’r’,encoding=’’utf8) as file:
response = file.read()
else:
status_code=’404 Not Found’
response = '页面走丢了’
start_response(‘status_code’,[(‘Content-Type,’text/html;charset=utf8’)])
return [‘response’.encode(‘utf8’)]
if_ name_=='_ main_ ':
httpd : make_server(‘’, 8080, demo_app):
sa = httpd.socket. getsockname()
print("Serving HTTP on", sa[0], "port", sa[1], "...")
httpd.serve_forever()
运行并访问：127.0.0.1:8080/test
访问结果如下：
这是装了插件以后的样子，这个插件在哪安装，更多工具里有个扩展程序，在扩展程序中的 Chrome 商店搜索 json 就能找到。
（2）读取并返回文件
写一个 html 文件，名为 hello.html。我写的大家看不懂，大家看效果就可以
效果如图：
修改代码：
from wsgiref.simple_server import make_server
def demo_app(environ,start_response):
path=environ[‘PATH_INFO’]
status_code=’200 OK’
if path == '/':
response =’欢迎来到我的首页'
elif path =='/test':
response = json.dumps({‘name’:’zhangsan’,’age’:18})
elif path == ‘/demo' :
with open(‘page/xxxx.txt’,’r’,encoding=’’utf8) as file:
response = file.read()
elif path == ‘/hello' :
with open(‘page/hello.html’,’r’,encoding=’’utf8) as file:
response = file.read()
else:
status_code=’404 Not Found’
response = '页面走丢了’
start_response(‘status_code’,[(‘Content-Type,’text/html;charset=utf8’)])
return [‘response’.encode(‘utf8’)]
if_ name_=='_ main_ ':
httpd : make_server(‘’, 8080, demo_app):
sa = httpd.socket. getsockname()
print("Serving HTTP on", sa[0], "port", sa[1], "...")
httpd.serve_forever()
运行并访问：127.0.0.1:8080/hello
访问结果如下：
3.前端给后端怎么传输数据：
访问时在地址栏加个问号输入传的数据
127.0.0.1:8080/hello?name=zhangsan &age=18,后端就能拿数据，用environ[‘QUERY_STRING’]拿数据
（1）代码：
from wsgiref.simple_server import make_server
def demo_app(environ,start_response):
path=environ[‘PATH_INFO’]
environ[‘QUERY_STRING’]
status_code=’200 OK’
if path == '/':
response =’欢迎来到我的首页'
elif path =='/test':
response = json.dumps({‘name’:’zhangsan’,’age’:18})
elif path == ‘/demo' :
with open(‘page/xxxx.txt’,’r’,encoding=’’utf8) as file:
response = file.read()
elif path == ‘/hello' :
with open(‘page/hello.html’,’r’,encoding=’’utf8) as file:
response = file.read()
else:
status_code=’404 Not Found’
response = '页面走丢了’
start_response(‘status_code’,[(‘Content-Type,’text/html;charset=utf8’)])
return [‘response’.encode(‘utf8’)]
if_ name_=='_ main_ ':
httpd : make_server(‘’, 8080, demo_app):
sa = httpd.socket. getsockname()
print("Serving HTTP on", sa[0], "port", sa[1], "...")
httpd.serve_forever()
运行发现，发的数据是能找到的
（2）怎么拿数据
代码：
from wsgiref.simple_server import make_server
def demo_app(environ,start_response):
path=environ[‘PATH_INFO’]
print(environ,file=open(‘pages/xxxx.txt’,’w’,encoding=’utf8’))
status_code=’200 OK’
if path == '/':
response =’欢迎来到我的首页'
elif path =='/test':
response = json.dumps({‘name’:’zhangsan’,’age’:18})
elif path == ‘/demo' :
with open(‘page/xxxx.txt’,’r’,encoding=’’utf8) as file:
response = file.read()
elif path == ‘/hello' :
with open(‘page/hello.html’,’r’,encoding=’’utf8) as file:
response = file.read()
else:
status_code=’404 Not Found’
response = '页面走丢了’
start_response(‘status_code’,[(‘Content-Type,’text/html;charset=utf8’)])
return [‘response’.encode(‘utf8’)]
if_ name_=='_ main_ ':
httpd : make_server(‘’, 8080, demo_app):
sa = httpd.socket. getsockname()
print("Serving HTTP on", sa[0], "port", sa[1], "...")
httpd.serve_forever()
运行后有[‘QUERY_STRING’]，这是字典
（3）print(environ.get(‘QUERY_STRING’))
QUERY_STRING==>获取到客户端GET请求方式传递过来的参数
代码：
from wsgiref.simple_server import make_server
def demo_app(environ,start_response):
path=environ[‘PATH_INFO’]
print(environ.get(‘QUERY_STRING’))
status_code=’200 OK’
if path == '/':
response =’欢迎来到我的首页'
elif path =='/test':
response = json.dumps({‘name’:’zhangsan’,’age’:18})
elif path == ‘/demo' :
with open(‘page/xxxx.txt’,’r’,encoding=’’utf8) as file:
response = file.read()
elif path == ‘/hello' :
with open(‘page/hello.html’,’r’,encoding=’’utf8) as file:
response = file.read()
else:
status_code=’404 Not Found’
response = '页面走丢了’
start_response(‘status_code’,[(‘Content-Type,’text/html;charset=utf8’)])
return [‘response’.encode(‘utf8’)]
if_ name_=='_ main_ ':
httpd : make_server(‘’, 8080, demo_app):
sa = httpd.socket. getsockname()
print("Serving HTTP on", sa[0], "port", sa[1], "...")
httpd.serve_forever()
运行就可以拿到数据
这是 GET 请求的数据获取方式，直接把参数放在地址栏里用?、&连接发消息
POST 请求数据的方式后面再说，POST 的内容是在请求体里。
4.后端给前端发消息
比如访问127.0.0.1:8080显示欢迎来到我的首页，这就是后端传的消息，访问其他的也是一样的。
我写一个文件 info.html 里面写有{username}，欢迎回来。
（1）添加代码：
from wsgiref.simple_server import make_server
def demo_app(environ,start_response):
path=environ[‘PATH_INFO’]
print(environ.get(‘QUERY_STRING’))
status_code=’200 OK’
if path == '/':
response =’欢迎来到我的首页'
elif path =='/test':
response = json.dumps({‘name’:’zhangsan’,’age’:18})
elif path == ‘/demo' :
with open(‘page/xxxx.txt’,’r’,encoding=’’utf8) as file:
response = file.read()
elif path == ‘/hello' :
with open(‘page/hello.html’,’r’,encoding=’’utf8) as file:
response = file.read()
elif path == ‘/info' :
#查询数据库，获取到用户名
name=’jack’
with open(‘page/info.html’,’r’,encoding=’’utf8) as file:
response = file.read()
else:
status_code=’404 Not Found’
response = '页面走丢了’
start_response(‘status_code’,[(‘Content-Type,’text/html;charset=utf8’)])
return [‘response’.encode(‘utf8’)]
if_ name_=='_ main_ ':
httpd : make_server(‘’, 8080, demo_app):
sa = httpd.socket. getsockname()
print("Serving HTTP on", sa[0], "port", sa[1], "...")
httpd.serve_forever()
（2）如果查询数据库名字叫jack，怎么显示名字 jack 在页面上呢。response 是读info 文件的，读出来之后就是一个内容就是一个文本，即字符串，有个字符串‘{username},欢迎回来’怎么把jack填进去：
from wsgiref.simple_server import make_server
response =’欢迎来到我的首页'
elif path =='/test':
elif path == ‘/info' :
#查询数据库，获取到用户名
name=’jack’
with open(‘page/info.html’,’r’,encoding=’’utf8) as file:
response = file.read().format(username=name)
#‘{username},欢迎回来’.format(username=name)
else:
status_code=’404 Not Found’
response = '页面走丢了’
start_response(‘status_code’,[(‘Content-Type,’text/html;charset=utf8’)])
return [‘response’.encode(‘utf8’)]
if_ name_=='_ main_ ':
httpd : make_server(‘’, 8080, demo_app):
sa = httpd.socket. getsockname()
print("Serving HTTP on", sa[0], "port", sa[1], "...")
httpd.serve_forever()
运行之后显示：jack，欢迎回来
（3）这个在后面不用写这么复杂，后面会有很多渲染模板，在讲flask、django都有模板，渲染引擎。
渲染引擎就是在页面上写很多空，在渲染时把空填上，这就是动态的页面了。
演示举例：
把info文件内容里的{username},欢迎回来，改成{username},欢迎回来，你今年{age}岁了，你的性别是{gender}。
修改代码：
from wsgiref.simple_server import make_server
def demo_app(environ,start_response):
path=environ[‘PATH_INFO’]
print(environ.get(‘QUERY_STRING’))
status_code=’200 OK’
if path == '/':
response =’欢迎来到我的首页'
elif path =='/test':
response = json.dumps({‘name’:’zhangsan’,’age’:18})
elif path == ‘/demo' :
with open(‘page/xxxx.txt’,’r’,encoding=’’utf8) as file:
response = file.read()
elif path == ‘/hello' :
with open(‘page/hello.html’,’r’,encoding=’’utf8) as file:
response = file.read()
elif path == ‘/info' :
#查询数据库，获取到用户名
name=’jack’
with open(‘page/info.html’,’r’,encoding=’’utf8) as file:
response=file.read().format(username=name ,age=18,gender=’男’)
#‘{username},欢迎回来’.format(username=name)
else:
status_code=’404 Not Found’
response = '页面走丢了’
start_response(‘status_code’,[(‘Content-Type,’text/html;charset=utf8’)])
return [‘response’.encode(‘utf8’)]
if_ name_=='_ main_ ':
httpd : make_server(‘’, 8080, demo_app):
sa = httpd.socket. getsockname()
print("Serving HTTP on", sa[0], "port", sa[1], "...")
httpd.serve_forever()
运行访问结果就是：jack，欢迎回来，你今年18岁了，你的性别是男
