Write your own filter¶
New in version 0.7.
Writing own filters is very easy. All you have to do is to subclass the Filter class and override the filter method. Additionally a filter is instantiated with some keyword arguments you can use to adjust the behavior of your filter.
As an example, we write a filter that converts all Name.Function tokens to normal Name tokens to make the output less colorful.
from pygments.util import get_bool_opt from pygments.token import Name from pygments.filter import Filter class UncolorFilter(Filter): def __init__(self, **options): Filter.__init__(self, **options) self.class_too = get_bool_opt(options, 'classtoo') def filter(self, lexer, stream): for ttype, value in stream: if ttype is Name.Function or (self.class_too and ttype is Name.Class): ttype = Name yield ttype, value
Some notes on the lexer argument: that can be quite confusing since it doesn’t need to be a lexer instance. If a filter was added by using the add_filter() function of lexers, that lexer is registered for the filter. In that case lexer will refer to the lexer that has registered the filter. It can be used to access options passed to a lexer. Because it could be None you always have to check for that case if you access it.
Using a decorator¶
You can also use the simplefilter decorator from the pygments.filter module:
from pygments.util import get_bool_opt from pygments.token import Name from pygments.filter import simplefilter @simplefilter def uncolor(self, lexer, stream, options): class_too = get_bool_opt(options, 'classtoo') for ttype, value in stream: if ttype is Name.Function or (class_too and ttype is Name.Class): ttype = Name yield ttype, value
You can instantiate this filter by calling uncolor(classtoo=True), the same way that you would have instantiated the previous filter by calling UncolorFilter(classtoo=True). Indeed, The decorator automatically ensures that uncolor is a class which subclasses an internal filter class. The class uncolo uses the decorated function as a method for filtering. (That’s why there is a self argument that you probably won’t end up using in the method.)