一、Form标签简介
首先要学习的是表格标签<form>
<form action ="/foo">
<input type = "text" name = "test">
<input type ="submit" value ="ClickOnMe">
</form>
- <form> 表格标签
- <form action ="url"> 表格所要提交的目的（where a form submit to）
- <input type ="text"> input为输入控件，text定义了该控件类型是文本框
- <input type ="submit"> intput为输入控件，submit定义了该空间类型是提交按钮，点击该按钮相当于按回车键
当输入123，然后点击ClickOnMe后，显示如下结果。
掌握了这些基本知识，就能够做一个简单的搜索框，让结果指向百度或者Google
<form action="http://www.baidu.com/s">
<input name="wd">
<input type="submit">
</form>
二、第一个应用程序：Suck World
先下载并安装GoogleAppEngine（自行百度），新建一个新的应用
import webapp2
class MainHandler(webapp2.RequestHandler):
def get(self):
self.response.write(‘Suck world!‘)
app = webapp2.WSGIApplication([
(‘/‘, MainHandler)
], debug=True)
- 当webapp2接受到一个对‘/‘（根路径）的请求时，会实例化MainHandler类，并调用get方法
- 关于请求的信息，包含在self.request中
- 如果遇到异常，debug=ture 会通知打印栈跟踪
接下来对程序进行修改，让它和知识点一最后给出的例子一样
import webapp2
# new string object from
form="""
<form action="http://www.baidu.com/s">
<input name="wd">
<input type="submit">
</form>
"""
#print form
class MainHandler(webapp2.RequestHandler):
def get(self):
#slef.resopne.headers[‘Content-Type‘] = ‘text/plain‘
self.response.write(form)
app = webapp2.WSGIApplication([
(‘/‘, MainHandler)
], debug=True)
GoogleApp自动将打印的信息当成html处理，如果你想打印纯文本，需要多添加一条：slef.resopne.headers[‘Content-Type‘] = ‘text/plain‘
接下来，我们让form的信息提交到自己创建的路径中，而不是提交到百度中
import webapp2
# new string object from
form="""
<form action="/testform">
<input name="wd">
<input type="submit">
</form>
"""
#print form
class MainHandler(webapp2.RequestHandler):
def get(self):
#slef.resopne.headers[‘Content-Type‘] = ""
self.response.write(form)
class TestHandler(webapp2.RequestHandler):
def get(self):
wd = self.request.get("wd")
self.response.write(wd)
app = webapp2.WSGIApplication([
(‘/‘, MainHandler),
(‘/testform‘,TestHandler)
], debug=True)
- form的信息提交给了“/formtest"，由于app只识别‘/‘，所以新建了一个(‘/testform‘,TestHandler)
- TestHandler类中包含了以下信息：新建一个wd对象，用于储存请求信息中wd变量的信息，然后做出回应，打印wd变量
也可以让浏览器打印所有请求信息
#!/usr/bin/env python
#
# Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
import webapp2
# new string object from
form="""
<form action="/testform">
<input name="wd">
<input type="submit">
</form>
"""
#print form
class MainHandler(webapp2.RequestHandler):
def get(self):
#self.response.headers[‘Content-Type‘] = ‘text/plain‘
self.response.write(form)
class TestHandler(webapp2.RequestHandler):
def get(self):
#wd = self.request.get("wd")
#self.response.write(wd)
self.response.headers[‘Content-Type‘] = ‘text/plain‘
self.response.write(self.request)
app = webapp2.WSGIApplication([
(‘/‘, MainHandler),
(‘/testform‘,TestHandler)
], debug=True)
接下来介绍form标签的post属性，也就是post方法
POST：向指定的资源提交要被处理的数据
# new string object from
form="""
<form method="post" action="/testform">
<input name="wd">
<input type="submit">
</form>
"""
#print form
class MainHandler(webapp2.RequestHandler):
def get(self):
#self.response.headers[‘Content-Type‘] = ‘text/plain‘
self.response.write(form)
class TestHandler(webapp2.RequestHandler):
def post(self):
wd = self.request.get("wd")
self.response.write(wd)
#self.response.headers[‘Content-Type‘] = ‘text/plain‘
#self.response.write(self.request)
app = webapp2.WSGIApplication([
(‘/‘, MainHandler),
(‘/testform‘,TestHandler)
], debug=True)
注意代码的两处改动，一个是在<form>标签中声明 method = post，也就是说，如果不声明，那么默认为get方法。另一处改动是TestHandler类的get方法要改名为post方法
Get vs Post
- get方法常用于获取某个文件；post方法用于更新数据
- get方法的参数保存在url中；post方法的参数保存在主体中
- get方法的参数有长度限制；post方法的参数没有长度限制
- get方法支持缓存，不必每次都请求；post方法不支持缓存
- get方法无法改变服务端；post方法可以改变服务端
三、认识更多的Form属性
password属性：能让输入的文本以星号显示，但是结果能会在url中显示
<form>
<input type="password" name="wd">
<input type="submit">
</form>
checkbox属性：多选按钮，如果点击按钮，参数会以name=on的形式显示在浏览器中，否则则不会显示参数
<form>
<input type="checkbox" name="wd">
<input type="checkbox" name="r">
<input type="checkbox" name="s">
<br>
<input type="submit">
</form>
radio属性：单选按钮控件，只需要为不同按钮赋予相同名字即可
<form>
<input type="radio" name="wd">
<input type="radio" name="wd">
<input type="ra" name="wd">
<br>
<input type="submit">
</form>
但是，单单使用radio属性的话，不管点击哪一个，结果的url中都不会有提示点击哪一个的信息，只会显示wd=on。这时候，就需要借助value属性
<form>
<input type="radio" name="wd" value="one">
<input type="radio" name="wd" value="two">
<input type="radio" name="wd" value="three">
<br>
<input type="submit">
</form>
选择第三个按钮，最终会在url上显示相关信息
label标签： input 元素定义标注（标记）
为上述按钮添加文本标注
<form>
<label>
One
<input type="radio" name="wd" value="one">
</label>
<label>
Two
<input type="radio" name="wd" value="two">
</label>
<label>
Three
<input type="radio" name="wd" value="three">
</label>
<br>
<input type="submit">
</form>
selcet：创建单选或者多选元素
<form>
<select name="q">
<option>one</option>
<option>two</option>
<option>three</option>
</select>
<br>
<input type="submit">
</form>
url的信息会以q=one（two或者three）的形式来显示
如果要改变url显示的信息，可以借助value
<form>
<select name="q">
<option value="1">one</option>
<option value="2">two</option>
<option value="3">three</option>
</select>
<br>
<input type="submit">
</form>
结果会以q=1（2或者3）的形式显示在url中
四、验证
验证服务端接受的内容是否是什么所期待的（what we receive is what we expect)
新建一个应用，让用户输入年/月/日
form="""
<form method="post">
what is your birthday?
<br>
<label> Month
<input type="text" name="month">
</label>
<label> Day
<input type="text" name="day">
</label>
<label> Year
<input type="text" name="year">
</label>
<br>
<input type="submit">
</form>
"""
class MainHandler(webapp2.RequestHandler):
def get(self):
self.response.write(form)
def post(self):
self.response.write("Thanks!")
app = webapp2.WSGIApplication([
(‘/‘, MainHandler)
], debug=True)
运行效果如下：
我们知道，年月日的输入是有限定的，可以采取两种方式对用户输入的数字进行限定：
- 用下拉列表的方式呈现所有合法的选项，供用户选择
- 对用户输入的信息进行验证
先编写对月份的验证
# judge the input of month is what we expect
#新建一个字典，来保存12个月的信息
months = [‘janurary‘,
‘February‘,
‘March‘,
‘April‘,
‘May‘,
‘june‘,
‘july‘,
‘August‘,
‘September‘,
‘October‘,
‘November‘,
‘December‘
]
def valid_month(month):
if month:
#将用户输入的月份的首字母大写化
cap_month = month.capitalize()
#遍历字典，看首字母大写化之后的月份是否在里面
if cap_month in months:
return cap_month
else:
print("not legal")
return None
可以稍微修改，只校验前三个字母即可
# judge the input of month is what we expect
months = [‘janurary‘,
‘February‘,
‘March‘,
‘April‘,
‘May‘,
‘june‘,
‘july‘,
‘August‘,
‘September‘,
‘October‘,
‘November‘,
‘December‘
]
month_abbvs = dict((m[:3].lower(), m) for m in months)
def valid_month(month):
if month:
short_month = month[:3].lower()
return month_abbvs.get(short_month)
对日期的验证较为简单，现在只是简单的验证，没有具体到某个月最大天数
def valid_day(day):
if day and day.isdigit():
day = int(day)
if day > 0 and day <= 31:
return day
对年份的验证和日期验证类似
def valid_year(year):
if year and year.isdigit():
year1 = int(year)
if year > 1900 and year <2020:
return year
接下来就可以将其整合到应用中了，先了解下整个验证的过程
- =》用户获取表格信息（get form）
- 《= 服务器返回表格页面（form date）
- =》用户提交表格信息（post date）
- 服务端对其进行验证：验证成功，返回感谢页面；验证失败，返回表格页面
也就是说，我们的验证机制应该包括三个方面的内容：
- 验证用户的输入是否合法
- 如果不合法的话，再次返回表格输入页面
- 提示错误信息
import webapp2
def valid_day(day):
if day and day.isdigit():
day = int(day)
if day > 0 and day <= 31:
return day
def valid_year(year):
if year and year.isdigit():
year = int(year)
if year > 1900 and year <2020:
return year
# judge the input of month is what we expect
months = [‘janurary‘,
‘February‘,
‘March‘,
‘April‘,
‘May‘,
‘june‘,
‘july‘,
‘August‘,
‘September‘,
‘October‘,
‘November‘,
‘December‘
]
month_abbvs = dict((m[:3].lower(), m) for m in months)
def valid_month(month):
if month:
short_month = month[:3].lower()
return month_abbvs.get(short_month)
form="""
<form method="post">
what is your birthday?
<br>
<label> Month
<input type="text" name="month">
</label>
<label> Day
<input type="text" name="day">
</label>
<label> Year
<input type="text" name="year">
</label>
<br>
<input type="submit">
</form>
"""
class MainHandler(webapp2.RequestHandler):
def get(self):
self.response.write(form)
def post(self):
user_month = valid_month(self.request.get(‘month‘))
user_day = valid_day(self.request.get(‘day‘))
user_year = valid_year(self.request.get(‘year‘))
# not x means if x is any kind of zero or empty container, or False...
if not (user_month and user_day and user_year):
self.response.write(form)
else:
self.response.write("Thanks! That‘s a totally valid date !")
app = webapp2.WSGIApplication([
(‘/‘, MainHandler)
], debug=True)
程序不过是按照刚才的分析来做，在post方法下添加了对用户数据输入的验证，然后判断是否合法，并根据不同判断返回不同信息。不过该程序还差一样提示错误信息。
先补充一个字符串替代的知识，共有三种方式可以在字符串中嵌入变量：
t1 = "I think %s is perfectly normal things to do in public"
def sub1(s):
return t1 %s
t2 = "I think %s and %s are perfectly normal things to do in public"
def sub2(s1,s2):
return t2 %(s1,s2)
t3 = "I‘m %(nickname)s. My real name is %(name)s, but my friend all call me %(nickname)s"
def sub_3(name, nickname):
return t3 %{‘name‘:name, ‘nickname‘:nickname}
除了提示错误信息之外，还增加了一个功能：当用户输入错误信息的时候，错误信息仍然显示在文本框里面，以避免用户需要全部重新输入一遍
import webapp2
def valid_day(day):
if day and day.isdigit():
day = int(day)
if day > 0 and day <= 31:
return day
def valid_year(year):
if year and year.isdigit():
year = int(year)
if year > 1900 and year <2020:
return year
# judge the input of month is what we expect
months = [‘janurary‘,
‘February‘,
‘March‘,
‘April‘,
‘May‘,
‘june‘,
‘july‘,
‘August‘,
‘September‘,
‘October‘,
‘November‘,
‘December‘
]
month_abbvs = dict((m[:3].lower(), m) for m in months)
def valid_month(month):
if month:
short_month = month[:3].lower()
return month_abbvs.get(short_month)
#嵌入了四个变量 month，day，year，error
form="""
<form method="post">
what is your birthday?
<br>
<label> Month
<input type="text" name="month" value="%(month)s">
</label>
<label> Day
<input type="text" name="day" value="%(day)s">
</label>
<label> Year
<input type="text" name="year" value="%(year)s">
</label>
<div style="color:red">%(error)s</div>
<br>
<input type="submit">
</form>
"""
class MainHandler(webapp2.RequestHandler):
#因为根据数据合法性所返回的结果是不同的，所以统一用一个函数编写
def write_form(self,error="",month="",day="",year=""):
self.response.write(form %{"error": error,
"month": month,
"day": day,
"year": year})
#step1：获取表格信息，四个变量不需要任何参数
def get(self):
self.write_form()
#setp2:用户提交表格信息
def post(self):
#获取用户输入信息
user_month = self.request.get(‘month‘)
user_day = self.request.get(‘day‘)
user_year = self.request.get(‘year‘)
#判断输入信息合法与否
month = valid_month(user_month)
day = valid_day(user_day)
year = valid_year(user_year)
# not x means if x is any kind of zero or empty container, or False...
if not (month and day and year):
#如果数据输入没有通过验证，除了返回错误信息外，还返回原来用户的输入信息
self.write_form("That donesn‘t look valid to me ,friend.",
user_month, user_day, user_year)
else:
self.response.write("Thanks! That‘s a totally valid date !")
app = webapp2.WSGIApplication([
(‘/‘, MainHandler)
], debug=True)
上述的程序仍然有bug，就是文本框无法对输入字符进行处理，例如，在月份那栏输入foo">drep!，结果显示如下
因为用户输入的">被当做特殊字符处理，所以才导致出错。我们需要用到转移字符。例如，要在浏览器打印<html>应该如何打印？正确方式是用 < 与 > 的转义字符来替代
What if i want to talk about <html> in html? What if i want to talk about <html>in html?
&：&；
<: <
>: >
" : "
那么，如何解决上述问题呢？
编写函数，用于将用户在文本框输入的内容转化成转义字符，python本身也有内置模块（cgi）直接支持
#import cgi
def escape_html(s):
#return cgi.escape(s,quote = True)
for(i,o) in (("&","&"),
(">",">"),
("<","<"),
(‘"‘,""")):
s = s.replace(i,o)
return s
然后重写write_form函数即可
def write_form(self,error="",month="",day="",year=""):
self.response.write(form %{"error": error,
"month": escape_html(month),
"day": escape_html(day),
"year": escape_html(year)})
五、重定向
当我们输入正确的日期时，会返回一个感谢界面
如果解决上述的两个问题？答案就是给对返回的页面进行重定向，包括以下三个步骤：
- 做一个“thank"的hander
- 添加 /thank的url
- 进行定向
# not x means if x is any kind of zero or empty container, or False...
if not (month and day and year):
self.write_form("That donesn‘t look valid to me ,friend.",
user_month, user_day, user_year)
else:
#进行定向
self.redirect("/thanks")
#添加Thank的Handler
class ThanksHandler(webapp2.RequestHandler):
def get(self):
self.response.write("Thanks! That‘s a totally valid date !")
#添加thank的url
app = webapp2.WSGIApplication([
(‘/‘, MainHandler),(‘/thanks‘,ThanksHandler)
], debug=True)
时间： 2024-11-05 20:32:19