python – Pyscopg DB – 错误向代码添加持久性

我正在研究Udacity的在线项目.我正在使用由他们配置的vagrant来运行包含数据库的服务器.不幸的是,当我试图给出代码持久性时,服务器每次都会返回一个错误.我是python的新手所以请原谅任何明显的错误.

这是错误：

Serving HTTP on port 8000...
Traceback (most recent call last):
  File "/usr/lib/python2.7/wsgiref/handlers.py", line 85, in run
    self.result = application(self.environ, self.start_response)
  File "forum.py", line 95, in Dispatcher
    return DISPATCH[page](env, resp)
  File "forum.py", line 68, in Post
    length = int(env.get('CONTENT_LENGTH', 0))
ValueError: invalid literal for int() with base 10: ''
10.0.2.2 - - [06/Jan/2016 04:44:16] "GET /post HTTP/1.1" 500 59
10.0.2.2 - - [06/Jan/2016 04:44:16] "GET /favicon.ico HTTP/1.1" 404 22

这是我在forumdb.py中更改的代码：

#
# Database access functions for the web forum.
# 

import psycopg2

## Database connection

def GetAllPosts():
    DB = psycopg2.connect("dbname=forum")
    c = DB.cursor()
    c.execute("SELECT time, content FROM posts ORDER BY time DESC")
    posts = ({'content': str(row[1]), 'time': str(row[0])}
             for row in c.fetchall())

    # This returns a dictionary -- returning just c.fetchall() will return a list of tuples

    DB.close()
    return posts

def AddPost(content):
    DB = psycopg2.connect("dbname=forum")
    c = DB.cursor()
    c.execute("INSERT INTO posts (content) values ('%s')" % content)
    DB.commit()
    DB.close()

forum.py – 此文件呈现html从DB：http:///ZiHWiiwr中提取数据

请帮忙 ！

解决方法:

您正在使用length = int(env.get(‘CONTENT_LENGTH’,0))(forum.py:68)查询WSGI环境.我刚刚运行了一个示例WSGI服务器(取自python docs的示例代码),它根据请求输出所有可用的环境变量：

from wsgiref.util import setup_testing_defaults
from wsgiref.simple_server import make_server

# A relatively simple WSGI application. It's going to print out the
# environment dictionary after being updated by setup_testing_defaults
def simple_app(environ, start_response):
    setup_testing_defaults(environ)

    status = '200 OK'
    headers = [('Content-type', 'text/plain')]

    start_response(status, headers)

    ret = ["%s: %s\n" % (key, value)
           for key, value in environ.iteritems()]
    return ret

httpd = make_server('', 8000, simple_app)
print "Serving on port 8000..."
httpd.serve_forever()

查询测试服务器时得到的输出是(在很多其他变量中)：

SERVER_PORT: 8000
CONTENT_LENGTH: 
GLADE_CATALOG_PATH: :

您看到CONTENT_LENGTH变量为空.这似乎也适用于您的应用程序.

如果现在使用env.get(‘CONTENT_LENGTH’,0)查询env-dictionary,实际上找到了CONTENT_LENGTH-key,但它的值是一个空字符串 – 这就是get()方法返回”而不是指定的原因默认值0.

由于空字符串无法转换为int,因此您将获得ValueError.

尝试捕获异常,您的代码应该工作：

try:
    length = int(env.get("CONTENT_LENGTH", 0))
except ValueError:
    length = 0

来源：http://www./content-1-203701.html