Docutils Transforms

Author:

David Goodger

Contact:
docutils-develop@lists.sourceforge.net
Revision:
8912
Date:
2021-12-23

Transforms change the document tree in-place, add to the tree, or prune it. Transforms resolve references and footnote numbers, process interpreted text, and do other context-sensitive processing. Each transform is a subclass of docutils.transforms.Transform.

There are transforms added by components, others (e.g. parts.Contents) are added by the parser, if a corresponding directive is found in the document.

To add a transform, components (objects inheriting from Docutils.Component like Readers, Parsers, Writers, Input, Output) overwrite the get_transforms() method of their base class. After the Reader has finished processing, the Publisher calls Transformer.populate_from_components() with a list of components and all transforms returned by the component's get_transforms() method are stored in a transformer object attached to the document tree.

For more about transforms and the Transformer object, see also PEP 258. (The default_transforms() attribute of component classes mentioned there is deprecated. Use the get_transforms() method instead.)

Transforms Listed in Priority Order

Transform classes each have a default_priority attribute which is used by the Transformer to apply transforms in order (low to high). The default priority can be overridden when adding transforms to the Transformer object.

Transform: module.Class

Added By

Priority

misc.class

"class" (d/p)

210

references.Substitutions

standalone (r), pep (r)

220

references.PropagateTargets

standalone (r), pep (r)

260

frontmatter.DocTitle

standalone (r)

320

frontmatter.DocInfo

standalone (r)

340

frontmatter.SectSubTitle

standalone (r)

350

peps.Headers

pep (r)

360

peps.Contents

pep (r)

380

universal.StripClasses...

Writer (w)

420

references.AnonymousHyperlinks

standalone (r), pep (r)

440

references.IndirectHyperlinks

standalone (r), pep (r)

460

peps.TargetNotes

pep (r)

520

references.TargetNotes

peps.TargetNotes (t/p)

0

misc.CallBack

peps.TargetNotes (t/p)

1

references.TargetNotes

"target-notes" (d/p)

540

references.Footnotes

standalone (r), pep (r)

620

references.ExternalTargets

standalone (r), pep (r)

640

references.InternalTargets

standalone (r), pep (r)

660

parts.SectNum

"sectnum" (d/p)

710

parts.Contents

"contents" (d/p), peps.Contents (t/p)

720

universal.StripComments

Reader (r)

740

peps.PEPZero

peps.Headers (t/p)

760

components.Filter

not used

780

universal.Decorations

Reader (r)

820

misc.Transitions

standalone (r), pep (r)

830

universal.ExposeInternals

Reader (r)

840

references.DanglingReferences

standalone (r), pep (r)

850

universal.SmartQuotes

Parser

855

universal.Messages

Writer (w)

860

universal.FilterMessages

Writer (w)

870

universal.TestMessages

DocutilsTestSupport

880

writer_aux.Compound

not used, to be removed

910

writer_aux.Admonitions

html4css1 (w), latex2e (w)

920

misc.CallBack

n/a

990

Key:

Transform Priority Range Categories

Priority

From

To

Category

0

99

immediate execution (added by another transform)

100

199

very early (non-standard)

200

299

very early

300

399

early

400

699

main

700

799

late

800

899

very late

900

999

very late (non-standard)

Transforms added by components

readers.Reader:
universal.Decorations,
universal.ExposeInternals,
universal.StripComments
readers.ReReader:

None

readers.standalone.Reader:
references.Substitutions,
references.PropagateTargets,
frontmatter.DocTitle,
frontmatter.SectionSubTitle,
frontmatter.DocInfo,
references.AnonymousHyperlinks,
references.IndirectHyperlinks,
references.Footnotes,
references.ExternalTargets,
references.InternalTargets,
references.DanglingReferences,
misc.Transitions
readers.pep.Reader:
references.Substitutions,
references.PropagateTargets,
references.AnonymousHyperlinks,
references.IndirectHyperlinks,
references.Footnotes,
references.ExternalTargets,
references.InternalTargets,
references.DanglingReferences,
misc.Transitions,
peps.Headers,
peps.Contents,
peps.TargetNotes
parsers.rst.Parser

universal.SmartQuotes

writers.Writer:
universal.Messages,
universal.FilterMessages,
universal.StripClassesAndElements
writers.UnfilteredWriter

None

writers.latex2e.Writer

writer_aux.Admonitions

writers.html4css1.Writer:

writer_aux.Admonitions

writers.odf_odt.Writer:

removes references.DanglingReferences