如何在Python的“美丽汤”中使用自定义解析器？

Question

我正在使用美汤4解析和修改一组HTML文件。HTML文件是角模板，这意味着它们的标记在某种程度上不同于常规HTML文档中的标记(混合大小写属性、指令、输入/输出绑定等)。

美丽汤文档 (html.parser，lxml，html5lib)中列出的解析器没有一个完全符合我的需求。最接近它的是在html.parser中构建的Python，但是我不得不对它做一些调整。

是否可以使用自定义解析器类与美丽汤？如果是，如何实施？

编辑:下面的是美丽汤如何解析模板的一个例子。主要问题是结果的所有属性都是小写(*ngIf -> *ngif)和指令(appAutoFocus、appKeepFocusInside等)。获取一个空字符串值(例如appautofocus="")。

from bs4 import BeautifulSoup

test_html = """
<kendo-dialog *ngIf="dialogOpened" appAutoFocus appKeepFocusInside (close)="closeDialog()" width="1000">
   <kendo-dialog-titlebar>A title</kendo-dialog-titlebar>
   <div *ngIf="model.showValidationFailedMessage" class="alert alert-danger alert-dismissible">
      <button type="button" class="close" aria-label="Close" (click)="model.closeValidationAlert()"><span
         aria-hidden="true">&amp;times;</span></button>
      Validation failed
   </div>

   <kendo-tabstrip [keepTabContent]="true">
      <kendo-tabstrip-tab title="Tab title 1" [selected]="true">
         <ng-template kendoTabContent>
            <div>Tab content</div>
         </ng-template>
      </kendo-tabstrip-tab>
   </kendo-tabstrip>
</kendo-dialog>
"""

document = BeautifulSoup(test_html, "html.parser")
print(document.prettify())

结果：

<kendo-dialog (close)="closeDialog()" *ngif="dialogOpened" appautofocus="" appkeepfocusinside="" width="1000">
 <kendo-dialog-titlebar>
  A title
 </kendo-dialog-titlebar>
 <div *ngif="model.showValidationFailedMessage" class="alert alert-danger alert-dismissible">
  <button (click)="model.closeValidationAlert()" aria-label="Close" class="close" type="button">
   <span aria-hidden="true">
    &amp;times;
   </span>
  </button>
  Validation failed
 </div>
 <kendo-tabstrip [keeptabcontent]="true">
  <kendo-tabstrip-tab [selected]="true" title="Tab title 1">
   <ng-template kendotabcontent="">
    <div>
     Tab content
    </div>
   </ng-template>
  </kendo-tabstrip-tab>
 </kendo-tabstrip>
</kendo-dialog>

Answer 1

您可以使用bs4.builder.register_treebuilders_from。内置构建器是bs4.builder包中的模块。例如，bs4.builder._lxml。

这是register_treebuilders_from。

def register_treebuilders_from(module):
    """Copy TreeBuilders from the given module into this module."""
    # I'm fairly sure this is not the best way to do this.
    this_module = sys.modules['bs4.builder']
    for name in module.__all__:
        obj = getattr(module, name)

        if issubclass(obj, TreeBuilder):
            setattr(this_module, name, obj)
            this_module.__all__.append(name)
            # Register the builder while we're at it.
            this_module.builder_registry.register(obj)

以及软件包根模块的尾部。

# Builders are registered in reverse order of priority, so that custom
# builder registrations will take precedence. In general, we want lxml
# to take precedence over html5lib, because it's faster. And we only
# want to use HTMLParser as a last result.
from . import _htmlparser
register_treebuilders_from(_htmlparser)
try:
    from . import _html5lib
    register_treebuilders_from(_html5lib)
except ImportError:
    # They don't have html5lib installed.
    pass
try:
    from . import _lxml
    register_treebuilders_from(_lxml)
except ImportError:
    # They don't have lxml installed.
    pass

因此，您需要创建一个带有bs4.builder.TreeBuilder子类的模块，并将其注册到模块的__all__中。然后将模块传递给register_treebuilders_from。