The Tag class and the parser classes support a method called insert. It works just like a Python list's insert method: it takes
an index to the tag's contents member, and sticks a new element in
that slot.
标签类和剖析类有一个insert方法，它就像Python列表的insert方法：
它使用索引来定位标签的contents成员，然后在那个位置插入一个新的元素。
This was demonstrated in the previous section, when we replaced a
tag in the document with a brand new tag. You can use insert to
build up an entire parse tree from scratch:
在前面那个小结中，我们在文档替换一个新的标签时有用到这个方法。你可以使用insert来重新构建整个剖析树：
from BeautifulSoup import BeautifulSoup, Tag, NavigableString
soup = BeautifulSoup()
tag1 = Tag(soup, "mytag")
tag2 = Tag(soup, "myOtherTag")
tag3 = Tag(soup, "myThirdTag")
soup.insert(0, tag1)
tag1.insert(0, tag2)
tag1.insert(1, tag3)
print soup
# <mytag><myOtherTag></myOtherTag><myThirdTag></myThirdTag></mytag>
text = NavigableString("Hello!")
tag3.insert(0, text)
print soup
# <mytag><myOtherTag></myOtherTag><myThirdTag>Hello!</myThirdTag></mytag>
An element can occur in only one place in one parse tree. If you
give insert an element that's already connected to a soup object, it
gets disconnected (with extract) before it gets connected
elsewhere. In this example, I try to insert my NavigableString into
a second part of the soup, but it doesn't get inserted again. It gets
moved:
一个元素可能只在剖析树中出现一次。如果你给insert的元素已经和soup对象所关联，
它会被取消关联(使用extract)在它在被连接别的地方之前。在这个例子中，我试着插入我的NavigableString到
soup对象的第二部分，但是它并没有被再次插入而是被移动了：
tag2.insert(0, text) print soup # <mytag><myOtherTag>Hello!</myOtherTag><myThirdTag></myThirdTag></mytag>
This happens even if the element previously belonged to a
completely different soup object. An element can only have one parent, one nextSibling, et cetera, so it can only be in one place
at a time.
即使这个元素属于一个完全不同的soup对象，还是会这样。
一个元素只可以有一个parent，一个nextSibling等等，也就是说一个地方只能出现一次。