# Reusing and extending Item Loaders

Item Loaders are designed to ease the maintenance burden of parsing rules, without losing flexibility and, at the same time, providing a convenient mechanism for extending and overriding them. For this reason Item Loaders support traditional Python class inheritance for dealing with differences in data schemas.

Suppose, for example, that you get some particular product names enclosed in three dashes (e.g. `---Plasma TV---`) and you don’t want to end up with those dashes in the final product names.

Here’s how you can remove those dashes by reusing and extending the default Product Item Loader (`ProductLoader`):

    from itemloaders.processors import MapCompose
    from myproject.loaders import ProductLoader

    def strip_dashes(x):
        return x.strip('-')

    class SiteSpecificLoader(ProductLoader):
        name_in = MapCompose(strip_dashes, ProductLoader.name_in)

Another case where extending Item Loaders can be very helpful is when you have multiple source formats, for example XML and HTML. In the XML version you may want to remove `CDATA` occurrences. Here’s an example of how to do it:

    from itemloaders.processors import MapCompose
    from myproject.ItemLoaders import ProductLoader
    from myproject.utils.xml import remove_cdata

    class XmlProductLoader(ProductLoader):
        name_in = MapCompose(remove_cdata, ProductLoader.name_in)

And that’s how you typically extend input/output processors.

There are many other possible ways to extend, inherit and override your Item Loaders, and different Item Loaders hierarchies may fit better for different projects. `itemloaders` only provides the mechanism; it doesn’t impose any specific organization of your Loaders collection - that’s up to you and your project’s needs.