launch_xml

This package provides an abstraction of the XML tree.

XML front-end mapping rules

Accessing xml attributes

When having an xml tag like:

<tag value="2"/>

If the entity e is wrapping it, the following statements will be true:

e.get_attr('value') == '2'
e.get_attr('value', data_type=int) == 2
e.get_attr('value', data_type=float) == 2.0

By default, the value of the attribute is returned as a string.

Allowed types are: - scalar types: str, int, float, bool - lists: Can be uniform like List[int], or non-uniform like List[Union[str, int]], List (same as list). In any case, the members should be of one of the scalar types. - An union of both any of the above. e.g.: Union[List[int], int]. - The list of entities type: List[Entity] (see below).

List is the usual object from the typing package. data_type can also be set to None, which works in the same way as passing:

Union[int, float, bool, list, str]

For handling lists, the *-sep attribute is used. e.g.:

<tag value="2,3,4" value-sep=","/>
<tag2 value="2 3 4" value-sep=" "/>
<tag3 value="2, 3, 4" value-sep=", "/>

tag.get_attr('value', data_type=List[int]) == [2, 3, 4]
tag2.get_attr('value', data_type=List[float]) == [2.0, 3.0, 4.0]
tag3.get_attr('value', data_type=List[str]) == ['2', '3', '4']

For checking if an attribute exists, use an optional argument:

value = e.get_attr('value', optional=True)
if value is not None:
    do_something(value)

With optional=False (default), AttributeError is raised if it is not found.

Accessing XML children as attributes:

In this xml:

<executable cmd="ls">
    <env name="a" value="100"/>
    <env name="b" value="stuff"/>
</node>

The env children could be accessed like:

env = e.get_attr('env', data_type=List[Entity])
len(env) == 2
env[0].get_attr('name') == 'a'
env[0].get_attr('value') == '100'
env[1].get_attr('name') == 'b'
env[1].get_attr('value') == 'stuff'

In these cases, e.env is a list of entities, that can be accessed in the same abstract way.

Accessing all the XML children:

All the children can be directly accessed:

e.children

It returns a list of launch_xml.Entity wrapping each of the XML children.

Built-in substitutions

See this document.

Changelog for package launch_xml

0.9.6 (2020-01-21)

0.9.5 (2019-11-13)

0.9.4 (2019-11-08)

0.9.3 (2019-10-23)

0.9.2 (2019-10-23)

• install resource marker file for packages (#341)
• Contributors: Dirk Thomas

0.9.1 (2019-09-25)

0.9.0 (2019-09-18)

• install package manifest (#330)
• Add deprecated argument to LaunchDescriptionn (#291)
• Add support for not optional environment variable substitution (#288)
• Add parsing methods for SetEnviromentVariable and UnsetEnviromentVariable (#272)
• Add parsing method for DeclareLaunchArgument (#270)
• Add frontend module in launch, launch_xml and launch_yaml packages (#226)
• Contributors: Dirk Thomas, ivanpauno