Read Using Object Filter

In read operation, YDK object is used as read filter. This document explains how to use YDK object as a read filter. Examples below use ydktest.json profile file to generate YDK test package. Let’s write some boilerplate code for device connection:

from ydk.services import CRUDService
from ydk.providers import NetconfServiceProvider
from ydk.models import ydktest_filterread as ysanity
ncc = NetconfServiceProvider(address='127.0.0.1',
                             username='admin',
                             password='admin',
                             protocol='ssh',
                             port=12022)
crud = CRUDService()

and ydk.services.CodecService to simplify payload comparison:

from ydk.services.codec_service import CodecService
from ydk.providers.codec_provider import CodecServiceProvider
codec = CodecService()
codec_provider = CodecServiceProvider(type='xml')

and configure the device with the initial data below:

a = ysanity.A()
a.a1, a.a2, a.a3 = "some value", "value of a2", "value of a3"
a.b.b1, a.b.b2, a.b.b3 = "some value", "value of b2", "value of b3"
a.b.f = a.b.F()
a.b.f.f1 = 'f'
a.b.c = a.b.C()
a.b.d.d1 = "some value d1"
a.b.d.d2 = "value of d2"
a.b.d.d3 = "value of d3"
a.b.d.e.e1, a.b.d.e.e2 = "some value e1", "value of e2"
l1, l2, l3 = a.Lst(), a.Lst(), a.Lst()
l1.number, l1.value = 1, "one"
l2.number, l2.value = 2, "two"
l3.number, l3.value = 3, "three"
a.lst.extend([l1, l2, l3])

crud.create(ncc, a)

The configuration above will config following data in device:

<a xmlns="http://cisco.com/ns/yang/ydk-filter">
  <a1>some value</a1>
  <a2>value of a2</a2>
  <a3>value of a3</a3>
  <b>
    <b1>some value</b1>
    <b2>value of b2</b2>
    <b3>value of b3</b3>
    <c/>
    <d>
      <d1>some value d1</d1>
      <d2>value of d2</d2>
      <d3>value of d3</d3>
      <e>
        <e1>some value e1</e1>
        <e2>value of e2</e2>
      </e>
    </d>
    <f>
      <f1>f</f1>
    </f>
  </b>
  <lst>
    <number>1</number>
    <value>one</value>
  </lst>
  <lst>
    <number>2</number>
    <value>two</value>
  </lst>
  <lst>
    <number>3</number>
    <value>three</value>
  </lst>
</a>

where <c> and <f> are presence container.

Read everything

The simplest filter is the top level container:

a_read = crud.read(ncc, ysanity.A())
print codec.encode(codec_provider, a_read)

the top level container filters nothing and return every data under current level:

<a xmlns="http://cisco.com/ns/yang/ydk-filter">
  <a1>some value</a1>
  <a2>value of a2</a2>
  <a3>value of a3</a3>
  <b>
    <b1>some value</b1>
    <b2>value of b2</b2>
    <b3>value of b3</b3>
    <c/>
    <d>
      <d1>some value d1</d1>
      <d2>value of d2</d2>
      <d3>value of d3</d3>
      <e>
        <e1>some value e1</e1>
        <e2>value of e2</e2>
      </e>
    </d>
    <f>
      <f1>f</f1>
    </f>
  </b>
  <lst>
    <number>1</number>
    <value>one</value>
  </lst>
  <lst>
    <number>2</number>
    <value>two</value>
  </lst>
  <lst>
    <number>3</number>
    <value>three</value>
  </lst>
</a>

Filter out more stuff

To make the filter more strict, you could assign more value to it. For example, if you are only interested in presence container C:

a = ysanity.A()
a.b.c = a.b.C()
a_read = crud.read(ncc, a)
print codec.encode(a_read)

<a xmlns="http://cisco.com/ns/yang/ydk-filter">
  <b>
    <c/>
  </b>
</a>

Content match nodes

According to NETCONF RFC, a “content match node” is used to select sibling nodes for filter output. Let’s try this concept with the following example:

a = ysanity.A()
a.b.b1 = "some value"
a_read = crud.read(ncc, a)
print codec.encode(codec_provider, a_read)

In the example show above, the a.b.b1 leaf serves as a content match node, therefore its siblings <b2> , <b3>, <c>, <d>, <f> and their children are all being kept.

<a xmlns="http://cisco.com/ns/yang/ydk-filter">
  <b>
    <b1>some value</b1>
    <b2>value of b2</b2>
    <b3>value of b3</b3>
    <c/>
    <d>
      <d1>some value d1</d1>
      <d2>value of d2</d2>
      <d3>value of d3</d3>
      <e>
        <e1>some value e1</e1>
        <e2>value of e2</e2>
      </e>
    </d>
    <f>
      <f1>f</f1>
    </f>
  </b>
</a>

Read on leaf

YDK also provides you with a READ class that could be used to read the value on a particular leaf. Let’s use this READ class and import it from ydk.types:

from ydk.types import READ
a = ysanity.A()
a.a1 = READ()
a_read = crud.read(ncc, a)
print codec.encode(codec_provider, a_read)

<a xmlns="http://cisco.com/ns/yang/ydk-filter">
  <a1>some value</a1>
</a>