JNCIA-DevOps Python And PyEZ Practice Test 1 — 15 Questions

Question 1

When managing configuration changes via PyEZ Config utility, which context manager ensures that changes are automatically rolled back if an exception occurs within the block?

Accepted Answer

with Config(dev) as cu:. The PyEZ Config utility provides a context manager that automatically handles locking, loading, committing, and rolling back changes if an exception occurs. The syntax 'with Config(dev) as cu:' opens a configuration session that, upon exiting the block, commits changes if no exception occurred, or rolls back if an exception was raised. This built-in behavior ensures atomic configuration changes.

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with Config(dev, mode='private') as cu:

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try: cu.lock() except: cu.rollback()

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cu.commit(rollback_on_error=True)

Question 2

When writing a Python script using PyEZ, how should you handle connection timeout exceptions when attempting to connect to an unreachable Junos device?

Accepted Answer

except ConnectError:. PyEZ raises ConnectError when it fails to establish a NETCONF session with the target device.

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except NetconfConnectionError:

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except DeviceOpenError:

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except socket.timeout:

Question 3

You are rendering a Jinja2 template in Python that includes a loop over a list of VLANs. Which Jinja2 block syntax correctly iterates over a list named 'vlan_list'?

Accepted Answer

{% for vlan in vlan_list %} ... {% endfor %}. Jinja2 uses `{% %}` delimiters for control-flow statements such as `for`, `if`, and `set`, and requires an explicit `{% endfor %}` to close the loop. The `{{ }}` syntax is reserved for expression output (printing values), so it cannot open a loop. Option C is the only choice that uses the correct statement delimiters and matching end tag.

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{{ for vlan in vlan_list }} ... {{ endfor }}

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[for vlan in vlan_list] ... [endfor]

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<% for vlan in vlan_list %> ... <% endif %>

Question 4

When configuring a JSNAPy test file, which section defines the specific RPCs or CLI commands that should be executed to gather operational data?

Accepted Answer

command: or rpc:. In a JSNAPy test file, the 'command:' or 'rpc:' section defines the specific CLI commands or RPCs to execute on the device to gather operational data. This section is part of the test definition and tells JSNAPy what data to collect for snapshotting and comparison.

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action:

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device_credentials:

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template:

Question 5

You need to write a Python script that extracts interface status from a Junos device using PyEZ and converts the XML output directly into a Python dictionary. Which utility or function can assist with this conversion?

Accepted Answer

Using PyEZ Table and View abstractions. PyEZ Table and View abstractions are designed to parse XML output from Junos devices into structured Python objects, including dictionaries. You define a View that maps XML elements to Python attributes, and a Table that uses the View to return a list of dictionaries. This is the idiomatic way to convert XML to Python data structures in PyEZ.

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dev.rpc.convert_to_dict()

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json.loads(dev.rpc.get_interface_information())

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etree.to_dict()

Question 6

When designing a custom PyEZ Table and View mapping in Python, what configuration parameter in the YAML definition file specifies the RPC or CLI command executed to gather the raw data?

Accepted Answer

rpc:. In a PyEZ Table/View YAML definition, the rpc: key specifies the Junos RPC (or CLI command) that the Table uses to retrieve raw data from the device. When the Table's get() method is called, PyEZ executes the RPC named under rpc: and passes the response to the View for parsing.

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get-rpc:

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exec:

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command_string:

Question 7

You are writing a script that uses PyEZ to load a Junos configuration file, but you want to replace an entire hierarchy level (e.g., protocols bgp) rather than merging the changes. Which parameter should you pass to the load method?

Accepted Answer

action='replace'. The action='replace' parameter tells PyEZ to replace the specified hierarchy level in the candidate configuration.

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overwrite=True

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merge=False

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mode='override'

Question 8

Which Python library does PyEZ depend on under the hood for managing secure SSH connections and NETCONF framing?

Accepted Answer

ncclient. PyEZ depends on ncclient under the hood for managing secure SSH connections and NETCONF framing. ncclient is a Python library that implements the NETCONF protocol and handles SSH transport, XML framing, and RPC execution. PyEZ wraps ncclient to provide a higher-level API for Junos devices.

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paramiko

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fabric

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netmiko

Question 9

When executing a PyEZ RPC call that returns a large dataset (e.g., massive routing table), how can you handle the output efficiently without exhausting local memory?

Accepted Answer

Using parser generators or iterator arguments supported by specific RPC wrappers. Using generators or streaming options in RPC handling prevents loading massive XML trees entirely into memory.

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etree.iterparse() directly on the raw socket stream

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dev.rpc.get_route_information(normalize=True)

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dev.stream_rpc()

Question 10

You are building a custom PyEZ application and need to catch exceptions specific to configuration parsing failures returned by Junos. Which exception class should your script import?

Accepted Answer

from jnpr.junos.exception import ConfigError. The jnpr.junos.exception module is the canonical location for all PyEZ exception classes, and ConfigError is the specific exception raised when Junos returns a configuration parsing or load failure (for example, a syntax error detected by the CLI/commit check). Importing it from jnpr.junos.exception allows the script to catch configuration-related failures distinctly from connection or RPC errors. This is the documented pattern in Juniper's PyEZ library for handling config load errors.

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from jnpr.junos.device import ConfigurationFailed

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from jnpr.junos.utils.config import ConfigError

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from jnpr.junos.exception import ParseError

Question 11

When working with the PyEZ Config utility, which THREE actions can be performed using the configuration context manager or its methods? (Choose three)

Accepted Answer

cu.validate(). Option B, cu.validate(), is correct because the PyEZ Config utility exposes a validate() method that checks the candidate configuration for syntax and commit-check errors before it is committed. Option C, cu.load(path='config.conf', format='text'), is correct because load() is the core method for loading configuration data into the candidate configuration, and it accepts parameters such as path and format (text, set, xml, or json). Option D, cu.rollback(), is correct because the Config utility provides rollback() to revert the candidate configuration to a previously committed configuration (for example, rollback(1) restores the last committed config). Option A, cu.gather_facts(), is not part of the Config utility; fact gathering is performed by the Device object (dev.facts or facts gathering via the Facts/Device classes). Option E, cu.upgrade_os(), is not a Config method; OS upgrades are handled by separate PyEZ utilities such as the SW package management classes, not the configuration context manager.

Answer

cu.gather_facts()

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cu.upgrade_os()

Question 12

When writing Jinja2 templates for Junos configurations, which THREE control flow or filtering constructs are valid? (Choose three)

Accepted Answer

{% for vlan in vlans %} ... {% endfor %}. Option C is correct because Jinja2 uses the {% for vlan in vlans %} ... {% endfor %} block syntax for iteration, which is the standard way to loop over a list such as VLANs when generating Junos configuration stanzas. Option D is correct because {% if ospf_enabled %} ... {% endif %} is the valid Jinja2 conditional block, allowing conditional inclusion of OSPF configuration based on a variable's truthiness. Option E is correct because {{ interface_list | map(attribute='name') | list }} uses Jinja2's expression delimiters {{ }} with valid filters: map(attribute='name') extracts the 'name' attribute from each item and list converts the generator into a list, a common pattern for building interface name lists. Option A is incorrect because [# ... #] is not Jinja2 delimiter syntax; Jinja2 uses {% %} for statements, and there is no 'foreach' keyword (the keyword is 'for'). Option B is incorrect because << ... >> is not Jinja2 delimiter syntax; conditionals must use {% if ... %} ... {% endif %} rather than angle-bracket tags.

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[# foreach item in list #] ... [# endfor #]

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<< if interface_active >> ... << endif >>

Question 13

Which TWO methods or attributes are valid when using the PyEZ SW utility to manage Junos software? (Choose two)

Accepted Answer

sw.install(remote_path='/var/tmp/image.tgz'). Option A is correct because the PyEZ SW utility's install() method accepts a remote_path argument pointing to the software image location on the device (e.g., /var/tmp/image.tgz), which is the standard way to install a Junos package already staged on the target device. Option B is correct because SW.upgrade() is a valid PyEZ method that takes a package parameter (the image filename) and a reboot flag to control whether the device reboots after the upgrade completes. Option C is not a valid PyEZ SW method; rollback is performed via the CLI (request system software rollback) or other RPCs, not sw.rollback_software(). Option D is not part of the SW utility; get_os_facts() is not a PyEZ SW method (OS facts are gathered through other means such as the Facts class). Option E is not a valid PyEZ SW method; commit_os() does not exist in the SW utility API.

Answer

sw.rollback_software()

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sw.get_os_facts()

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sw.commit_os()

Question 14

When configuring JSNAPy, which THREE components or sections are typically required within a YAML check/snapshot file? (Choose three)

Accepted Answer

command: or rpc: specifying the operational commands to run. Option A is correct because a JSNAPy snapshot/check YAML file must include a command: or rpc: key that lists the operational CLI commands or NETCONF RPCs to execute on the device. Option B is correct because the file requires a dev: or device: section that specifies the target device connection details (host, user, password, port, and connection method) used to reach the Junos device. Option E is correct because the action: key defines the test parameters and the operation mode, such as snap for capturing a snapshot or check for comparing against a reference snapshot. Option C is not required because jinja_template is not a mandatory JSNAPy section for defining checks or snapshots. Option D is not required because candidate_database and NETCONF lock parameters are not part of the standard required JSNAPy YAML structure.

Answer

jinja_template: defining external configuration templates

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candidate_database: defining NETCONF lock parameters

Question 15

Which TWO methods are valid for loading configuration data into the PyEZ Config utility from different sources? (Choose two)

Accepted Answer

cu.load(text='set system hostname router1', format='set'). Option A is correct because the PyEZ Config utility's load() method accepts a 'text' parameter containing configuration data in a specified format, and passing format='set' with a set-style command such as 'set system hostname router1' is a valid way to load configuration from an inline string. Option E is correct because load() also accepts a 'path' parameter pointing to a configuration file on disk, and specifying format='xml' correctly indicates that the file contains XML-format configuration data. Option B is incorrect because loading a Jinja2 template is done through the Template class (or template-related parameters), not by passing template_file and engine to Config.load(). Option C is incorrect because 'database' is not a valid load() parameter for selecting a configuration source; the Config utility loads data from strings, files, or templates, not by naming a database. Option D is incorrect because 'action' is not a load() parameter; committing changes is performed with the commit() method (or commit_check()), not by passing action='commit' to load().

Answer

cu.load(template_file='config.j2', engine='jinja2')

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cu.load(database='active')

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cu.load(action='commit')