Handling custom defined tags in StationXML with the Obspy Inventory
StationXML allows use of custom elements in addition to the ‘usual’ information defined by the StationXML standard. It allows a) custom namespace attributes to StationXML namespace tags and b) custom namespace subtags to StationXML namespace elements. ObsPy can handle both basic custom tags in all main elements (Network, Station, Channel, etc.) (a) and custom attributes (b) during input/output to/from StationXML. The following basic example illustrates how to output a StationXML file that contains additional xml tags/attributes:
from obspy import Inventory, UTCDateTime
from obspy.core.inventory import Network
from obspy.core.util import AttribDict
extra = AttribDict({
'my_tag': {
'value': True,
'namespace': 'http://some-page.de/xmlns/1.0',
'attrib': {
'{http://some-page.de/xmlns/1.0}my_attrib1': '123.4',
'{http://some-page.de/xmlns/1.0}my_attrib2': '567'
}
},
'my_tag_2': {
'value': u'True',
'namespace': 'http://some-page.de/xmlns/1.0'
},
'my_tag_3': {
'value': 1,
'namespace': 'http://some-page.de/xmlns/1.0'
},
'my_tag_4': {
'value': UTCDateTime('2013-01-02T13:12:14.600000Z'),
'namespace': 'http://test.org/xmlns/0.1'
},
'my_attribute': {
'value': 'my_attribute_value',
'type': 'attribute',
'namespace': 'http://test.org/xmlns/0.1'
}
})
inv = Inventory([Network('XX')], 'XX')
inv[0].extra = extra
inv.write('my_inventory.xml', format='STATIONXML',
nsmap={'my_ns': 'http://test.org/xmlns/0.1',
'somepage_ns': 'http://some-page.de/xmlns/1.0'})
All custom information to be stored in the customized StationXML has to
be stored in form of a dict or
AttribDict
object as the extra attribute of the object that should carry the
additional custom information (e.g. Network, Station, Channel). The
keys are used as the name of the xml tag, the content of the xml tag is defined
in a simple dictionary: 'value' defines the content of the tag (the string
representation of the object gets stored in the textual xml output).
'namespace' has to specify a custom namespace for the tag.
'type' can be used to specify whether the extra information should be
stored as a subelement ('element', default) or as an attribute
('attribute'). Attributes to custom subelements can be provided in form of
a dictionary as 'attrib'.
If desired for better (human-)readability, namespace abbreviations in the
output xml can be specified during output as StationXML by providing a dictionary
of namespace abbreviation mappings as nsmap parameter to
Inventory.write().
The xml output of the above example looks like:
<?xml version='1.0' encoding='UTF-8'?>
<FDSNStationXML xmlns:my_ns="http://test.org/xmlns/0.1" xmlns:somepage_ns="http://some-page.de/xmlns/1.0" xmlns="http://www.fdsn.org/xml/station/1" schemaVersion="1.0">
<Source>XX</Source>
<Module>ObsPy 1.0.2</Module>
<ModuleURI>https://www.obspy.org</ModuleURI>
<Created>2016-10-17T18:32:28.696287+00:00</Created>
<Network code="XX">
<somepage_ns:my_tag somepage_ns:my_attrib1="123.4" somepage_ns:my_attrib2="567">True</somepage_ns:my_tag>
<my_ns:my_tag_4>2013-01-02T13:12:14.600000Z</my_ns:my_tag_4>
<my_ns:my_attribute>my_attribute_value</my_ns:my_attribute>
<somepage_ns:my_tag_2>True</somepage_ns:my_tag_2>
<somepage_ns:my_tag_3>1</somepage_ns:my_tag_3>
</Network>
</FDSNStationXML>
When reading the above xml again, using
read_inventory(), the custom tags get
parsed and attached to the respective Network type objects (in this example to
the Inventory object) as .extra.
Note that all values are read as text strings:
from obspy import read_inventory
inv = read_inventory('my_inventory.xml')
print(inv[0].extra)
AttribDict({
u'my_tag': AttribDict({
'attrib': {
'{http://some-page.de/xmlns/1.0}my_attrib2': '567',
'{http://some-page.de/xmlns/1.0}my_attrib1': '123.4'
},
'namespace': 'http://some-page.de/xmlns/1.0',
'value': 'True'
}),
u'my_tag_4': AttribDict({
'namespace': 'http://test.org/xmlns/0.1',
'value': '2013-01-02T13:12:14.600000Z'
}),
u'my_attribute': AttribDict({
'namespace': 'http://test.org/xmlns/0.1',
'value': 'my_attribute_value'
}),
u'my_tag_2': AttribDict({
'namespace': 'http://some-page.de/xmlns/1.0',
'value': 'True'
}),
u'my_tag_3': AttribDict({
'namespace': 'http://some-page.de/xmlns/1.0',
'value': '1'
})
})
Custom tags can be nested:
from obspy import Inventory
from obspy.core.inventory import Network
from obspy.core.util import AttribDict
ns = 'http://some-page.de/xmlns/1.0'
my_tag = AttribDict()
my_tag.namespace = ns
my_tag.value = AttribDict()
my_tag.value.my_nested_tag1 = AttribDict()
my_tag.value.my_nested_tag1.namespace = ns
my_tag.value.my_nested_tag1.value = 1.23E+10
my_tag.value.my_nested_tag2 = AttribDict()
my_tag.value.my_nested_tag2.namespace = ns
my_tag.value.my_nested_tag2.value = True
inv = Inventory([Network('XX')], 'XX')
inv[0].extra = AttribDict()
inv[0].extra.my_tag = my_tag
inv.write('my_inventory.xml', format='STATIONXML',
nsmap={'somepage_ns': 'http://some-page.de/xmlns/1.0'})
This will produce an xml output similar to the following:
<?xml version='1.0' encoding='UTF-8'?>
<FDSNStationXML xmlns:somepage_ns="http://some-page.de/xmlns/1.0" xmlns="http://www.fdsn.org/xml/station/1" schemaVersion="1.0">
<Source>XX</Source>
<Module>ObsPy 1.0.2</Module>
<ModuleURI>https://www.obspy.org</ModuleURI>
<Created>2016-10-17T18:45:14.302265+00:00</Created>
<Network code="XX">
<somepage_ns:my_tag>
<somepage_ns:my_nested_tag1>12300000000.0</somepage_ns:my_nested_tag1>
<somepage_ns:my_nested_tag2>True</somepage_ns:my_nested_tag2>
</somepage_ns:my_tag>
</Network>
</FDSNStationXML>
The output xml can be read again using
read_inventory() and the nested tags can be
retrieved in the following way:
from obspy import read_inventory
inv = read_inventory('my_inventory.xml')
print(inv[0].extra.my_tag.value.my_nested_tag1.value)
print(inv[0].extra.my_tag.value.my_nested_tag2.value)
12300000000.0
True