Module 03: Jinja2

#!/usr/bin/python
from jinja2 import Template

template_string = "Hello {{ user }}"
my_template = Template(template_string)
result = my_template.render({"user": "lab"})
print(result)

‘templates’ is the path to the directory where the templates reside. The filename given to ‘get_template’ is now relative to the FileSystemLoader’s directory. This is the recommended way to load templates from files with Jinja2.

#!/usr/bin/python
from jinja2 import Environment, FileSystemLoader

env = Environment(loader=FileSystemLoader("templates"))
my_template = env.get_template("hello.j2")
result = my_template.render({"user": "lab"})
print(result)


#!/usr/bin/python
from jinja2 import Environment, FileSystemLoader

env = Environment(loader=FileSystemLoader("templates"))
my_template = env.get_template("hello.j2")

with open("variables/data.yml") as f:
    data = load(f)

result = my_template.render(data)
print(result)

Jinja2 Syntax

{# this is a comment #}

{%- for user in users %}
{% endfor %}

To access fields in a dictionary, use dictionary[‘field’] or dictionary.field .

To loop over items in a list, use;

{% for user in users %}

To loop over keys and values in a dictionary, use;

{%- for key, value in dictionary.items() %}

Conditional statement;

{%- if interface != 'fxp0.0' %}
{%- endif %}

{%- if var is defined %}

Variables can be modified by filters. ‘lower’ converts a variable to lower case.

{{ interface_id | lower }}

‘include’ can include other Jinja2 templates. It can be used to load different templates depending on the value of a variable. The ‘ignore missing’ option can be used to surpress errors if the requested template file is missing.

The ‘set’ directive can set template variables from within the template code.

YAML Syntax

---
interfaces:
- name: ge-0/0/0
  address: 172...
- name: ge-0/0/1
  address: 172...