为什么使用IMDbPY时会收到这么多警告和错误？

Question

我正在使用IMDbPY从IMDb获取数据。结果是正确的，一切看起来都没问题，只有一件事让我困扰：无论我怎么做，都会收到一些警告。虽然结果没问题，但这些结果总是在一长串警告和有时的错误之后才显示出来。

举个例子：下面的代码应该打印出《落水狗》（1992）：

import imdb
db = imdb.IMDb()
movie_obj = db.search_movie('pulp fiction')[0]
db.update(movie_obj)
print movie_obj['long imdb canonical title']

它确实打印出来了，但在此之前却出现了以下的警告和错误：

2011-03-18 00:33:11,490 WARNING [imdbpy.parser.http.domparser] C:\Python27\lib\site-packages\imdb\parser\http\utils.py:459: unable to use "lxml": No module named lxml.html
2011-03-18 00:33:11,507 WARNING [imdbpy.parser.http.domparser] C:\Python27\lib\site-packages\imdb\parser\http\utils.py:450: falling back to "beautifulsoup"
2011-03-18 00:33:13,483 WARNING [imdbpy.parser.http.domparser] C:\Python27\lib\site-packages\imdb\parser\http\utils.py:459: unable to use "lxml": No module named lxml.html
2011-03-18 00:33:13,483 WARNING [imdbpy.parser.http.domparser] C:\Python27\lib\site-packages\imdb\parser\http\utils.py:450: falling back to "beautifulsoup"
2011-03-18 00:33:15,137 ERROR [imdbpy.parser.http.domparser] C:\Python27\lib\site-packages\imdb\parser\http\utils.py:566: DOMHTMLMovieParser: caught exception extracting XPath "//div[@id='tn15title']//span[starts-with(text(), 'TV series')]"
Traceback (most recent call last):
  File "C:\Python27\lib\site-packages\imdb\parser\http\utils.py", line 555, in xpath
    xpath_result = element.xpath(path)
  File "C:\Python27\lib\site-packages\imdb\parser\http\bsouplxml\etree.py", line 57, in xpath
    return path.apply(node)
  File "C:\Python27\lib\site-packages\imdb\parser\http\bsouplxml\bsoupxpath.py", line 113, in apply
    nodes = step.apply(nodes)
  File "C:\Python27\lib\site-packages\imdb\parser\http\bsouplxml\bsoupxpath.py", line 287, in apply
    found = filter(checker, found)
  File "C:\Python27\lib\site-packages\imdb\parser\http\bsouplxml\bsoupxpath.py", line 331, in __call__
    return self.__filter(node)
  File "C:\Python27\lib\site-packages\imdb\parser\http\bsouplxml\bsoupxpath.py", line 360, in __starts_with
    first = node.contents[0]
IndexError: list index out of range
2011-03-18 00:33:16,785 WARNING [imdbpy.parser.http.domparser] C:\Python27\lib\site-packages\imdb\parser\http\utils.py:459: unable to use "lxml": No module named lxml.html
2011-03-18 00:33:16,785 WARNING [imdbpy.parser.http.domparser] C:\Python27\lib\site-packages\imdb\parser\http\utils.py:450: falling back to "beautifulsoup"
2011-03-18 00:33:16,849 WARNING [imdbpy.parser.http.domparser] C:\Python27\lib\site-packages\imdb\parser\http\utils.py:459: unable to use "lxml": No module named lxml.html
2011-03-18 00:33:16,849 WARNING [imdbpy.parser.http.domparser] C:\Python27\lib\site-packages\imdb\parser\http\utils.py:450: falling back to "beautifulsoup"

为什么会这样呢？我是不是做错了什么？

Answer 1

这个问题其实很简单明了：

无法使用 "lxml"：没有名为 lxml.html 的模块

你可以这样检查一下这个模块是否存在：

1. 在终端或命令提示符中，输入 python 并运行。
2. 把第一行的输出结果发出来（比如 Python 2.6.6 (r266...）。
3. 在这个命令行界面中，输入 import lxml。
4. 接着，尝试输入 import lxml.html。

对我来说，结果是这样的：

blender@desktop:~$ python
Python 2.6.6 (r266:84292, Sep 15 2010, 16:22:56) 
[GCC 4.4.5] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import lxml
>>> import lxml.html
>>> 

我已经安装了这个模块，所以没有任何输出（成功导入了）。