小编pbm*_*pbm的帖子

我将带有ForeignKey的SubForum类转换为自我父级:

class Forum(models.Model):
    name = models.CharField(max_length=200)
    url = models.URLField()

class SubForum(models.Model):
    name = models.CharField(max_length=200)
    orginal_id = models.IntegerField()

    forum = models.ForeignKey('Forum')
    parent = models.ForeignKey('self', null=True, blank=True)

我想允许null和空白的enteries - 我看到了一些例子,这是一种正确的方法.

在sql视图中一切正常:

BEGIN;CREATE TABLE "main_forum" (
    "id" integer NOT NULL PRIMARY KEY,
    "name" varchar(200) NOT NULL,
    "url" varchar(200) NOT NULL
)
;
CREATE TABLE "main_subforum" (
    "id" integer NOT NULL PRIMARY KEY,
    "name" varchar(200) NOT NULL,
    "orginal_id" integer NOT NULL,
    "forum_id" integer NOT NULL REFERENCES "main_forum" ("id"),
    "parent_id" integer
)
;COMMIT;

在parent_id …

我如何在XPath 1.0中找到所有空行col name="POW"？

<row>
<col name="WOJ">02</col>
<col name="POW"/>
<col name="GMI"/>
<col name="RODZ"/>
<col name="NAZWA">DOLNO?L?SKIE</col>
<col name="NAZDOD">województwo</col>
<col name="STAN_NA">2011-01-01</col>
</row>

我试过很多解决方案.在Firefox扩展XPath Checker选择中很少次,但lxml.xpath()表示表达式无效或只返回没有行.

我的Python代码:

from lxml import html
f = open('TERC.xml', 'r')
page = html.fromstring(f.read())
for r in page.xpath("//row[col[@name = 'POW' and not(text())]]"):
    print r.text_content()
    print "-------------------------"