在一个apache2/flask服务器上，有一个文件夹结构如下：

/var/www/myapp
/var/www/myapp/routing.py
/var/www/myapp/__init__.py
/var/www/wsgi-scripts/myapp.wsgi

myapp文件夹中的应用程序文件(routing.py)如下：

from flask import Flask, render_template
app = Flask(__name__)


@app.route('/')
def welkom():
    return render_template('welkom.html')


if __name__ == '__main__':
    app.debug = 'True'
    app.run()

wsgi-scripts中的myapp.wsgi文件如下：

import sys
sys.path.insert(0, '/var/www/myapp')
from myapp import routing as application

但是当我加载页面时，日志中出现以下错误：

[Fri Mar 15 08:06:32 2013] [error] [client 192.168.1.11] mod_wsgi (pid=23574): Target WSGI script '/var/www/wsgi-scripts/myapp.wsgi' cannot be loaded as Python module.
[Fri Mar 15 08:06:32 2013] [error] [client 192.168.1.11] mod_wsgi (pid=23574): Exception occurred processing WSGI script '/var/www/wsgi-scripts/myapp.wsgi'.
[Fri Mar 15 08:06:32 2013] [error] [client 192.168.1.11] Traceback (most recent call last):
[Fri Mar 15 08:06:32 2013] [error] [client 192.168.1.11]   File "/var/www/wsgi-scripts/myapp.wsgi", line 3, in <module>
[Fri Mar 15 08:06:32 2013] [error] [client 192.168.1.11]     import myapp.routing as application
[Fri Mar 15 08:06:32 2013] [error] [client 192.168.1.11] ImportError: No module named myapp.routing
[Fri Mar 15 08:06:32 2013] [error] [client 192.168.1.11] mod_wsgi (pid=23575): Target WSGI script '/var/www/wsgi-scripts/myapp.wsgi' cannot be loaded as Python module.
[Fri Mar 15 08:06:32 2013] [error] [client 192.168.1.11] mod_wsgi (pid=23575): Exception occurred processing WSGI script '/var/www/wsgi-scripts/myapp.wsgi'.
[Fri Mar 15 08:06:32 2013] [error] [client 192.168.1.11] Traceback (most recent call last):
[Fri Mar 15 08:06:32 2013] [error] [client 192.168.1.11]   File "/var/www/wsgi-scripts/myapp.wsgi", line 3, in <module>
[Fri Mar 15 08:06:32 2013] [error] [client 192.168.1.11]     import myapp.routing as application
[Fri Mar 15 08:06:32 2013] [error] [client 192.168.1.11] ImportError: No module named myapp.routing
[Fri Mar 15 08:06:33 2013] [error] [client 192.168.1.11] mod_wsgi (pid=23577): Target WSGI script '/var/www/wsgi-scripts/myapp.wsgi' cannot be loaded as Python module.
[Fri Mar 15 08:06:33 2013] [error] [client 192.168.1.11] mod_wsgi (pid=23577): Exception occurred processing WSGI script '/var/www/wsgi-scripts/myapp.wsgi'.
[Fri Mar 15 08:06:33 2013] [error] [client 192.168.1.11] Traceback (most recent call last):
[Fri Mar 15 08:06:33 2013] [error] [client 192.168.1.11]   File "/var/www/wsgi-scripts/myapp.wsgi", line 3, in <module>
[Fri Mar 15 08:06:33 2013] [error] [client 192.168.1.11]     import myapp.routing as application
[Fri Mar 15 08:06:33 2013] [error] [client 192.168.1.11] ImportError: No module named myapp.routing
[Fri Mar 15 08:06:33 2013] [error] [client 192.168.1.11] mod_wsgi (pid=23573): Target WSGI script '/var/www/wsgi-scripts/myapp.wsgi' cannot be loaded as Python module.
[Fri Mar 15 08:06:33 2013] [error] [client 192.168.1.11] mod_wsgi (pid=23573): Exception occurred processing WSGI script '/var/www/wsgi-scripts/myapp.wsgi'.
[Fri Mar 15 08:06:33 2013] [error] [client 192.168.1.11] Traceback (most recent call last):
[Fri Mar 15 08:06:33 2013] [error] [client 192.168.1.11]   File "/var/www/wsgi-scripts/myapp.wsgi", line 3, in <module>
[Fri Mar 15 08:06:33 2013] [error] [client 192.168.1.11]     import myapp.routing as application
[Fri Mar 15 08:06:33 2013] [error] [client 192.168.1.11] ImportError: No module named myapp.routing

2、解决方案

问题的原因是Python从wsgi导入失败，可能是因为以下原因：

1. myapp.routing模块没有被正确导入。
2. myapp.routing模块没有被正确定义。

方法一：

第一个答案中给出的解决方案是：

1. 直接导入routing模块，而不是myapp.routing模块。
2. 将application定义为一个函数，而不是一个模块。

代码示例：

# myapp.wsgi
import sys
sys.path.insert(0, '/var/www/myapp')

from routing import app as application

# routing.py
def app(environ, start_response):
    app.debug = 'True'
    app.run()

方法二：

第二个答案中给出的解决方案是：

1. 使用site.addsitedir()函数将myapp目录添加到Python的包路径中。
2. 使用sys.path[:] = new_sys_path将新路径放在Python的包路径的前面。

代码示例：

# myapp.wsgi
ALLDIRS = ['/var/www/myapp/']

import sys 
import site 

# Remember original sys.path.
prev_sys_path = list(sys.path) 

# Add each new site-packages directory.
for directory in ALLDIRS:
  site.addsitedir(directory)

# Reorder sys.path so new directories at the front.
new_sys_path = [] 
for item in list(sys.path): 
    if item not in prev_sys_path: 
        new_sys_path.append(item) 
        sys.path.remove(item) 
sys.