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python-sld

A python library for reading, writing, and manipulating SLD files.

Requirements

The lxml library is required for XML parsing and XML Schema validation. This requirement is listed in requirements.txt, and may be installed using pip with this command:

> sudo pip install -r requirements.txt

Installation

> easy_install python-sld

OR

> pip install python-sld

Usage

Using python-sld to create SLD documents is as easy as instantiating a StyledLayerDescriptor class object.

from sld import StyledLayerDescriptor
mysld = StyledLayerDescriptor()

You may also read an existing SLD document in by passing it as a parameter:

from sld import StyledLayerDescriptor
mysld = StyledLayerDescriptor('mysld.sld')

Addition of most elements are performed on the parent element, since they are related to parent nodes in order to preserve compliance:

nl = mysld.create_namedlayer()
ustyle = nl.create_style()

A couple class objects represent collections of nodes, such as Rules and CssParameters. They are properties of their parent classes (FeatureTypeStyle and Fill/Stroke/Font respectively). They behave as python lists, and you can access any of their items using a python list pattern:

fts = ustyle.create_featuretypestyle()
rule1 = fts.Rules[0]
print len(fts.Rules)
fts.Rules[0] = rule1

Filter objects are pythonic, and when combined with the '+' operator, they become ogc:And filters. When combined with the '|' operator, they become ogc:Or filters.

from sld import Filter

filter_1 = Filter(rule)
# set filter 1 properties

filter_2 = Filter(rule)
# set filter 2 properties

rule.Filter = filter_1 + filter_2

You may also construct a filter from an expression when using the create_filter method on the Rule object:

filter = rule.create_filter('population', '>', '100')

Implementation

At the current time, python-sld does ''not'' support the full SLD specification. The current implementation supports the following SLD elements:

  • StyledLayerDescriptor
  • NamedLayer
  • Name (of NamedLayer)
  • UserStyle
  • Title (of UserStyle and Rule)
  • Abstract
  • FeatureTypeStyle
  • Rule
  • ogc:Filter
  • ogc:And
  • ogc:Or
  • ogc:PropertyIsNotEqualTo
  • ogc:PropertyIsLessThan
  • ogc:PropertyIsLessThanOrEqualTo
  • ogc:PropertyIsEqualTo
  • ogc:PropertyIsGreaterThanOrEqualTo
  • ogc:PropertyIsGreaterThan
  • ogc:PropertyIsLike
  • ogc:PropertyName
  • ogc:Literal
  • MinScaleDenominator
  • MaxScaleDenominator
  • PointSymbolizer
  • LineSymbolizer
  • PolygonSymbolizer
  • TextSymbolizer
  • Mark
  • Graphic
  • Fill
  • Stroke
  • Font
  • CssParameter

Support

If you have any problems or questions, please visit the python-sld project on github: https://github.com/azavea/python-sld/

Contributors

@ewsterrenburg