jinja2 template + python

Owned by Jean-luc KRIKER
Last updated: Feb 14, 2019
2 min read


Rendering is changing data into something <variable> ------->  into "value". 

Parsing takes raw data or input and converts it a data structure, or structures that can be analyzed. 


Jinja2 - 101 - Intro to Jinja2 template building


Manual:   https://media.readthedocs.org/pdf/jinja2/latest/jinja2.pdf





jinja2 module
 With Python: ( use extensively by Ansible)

>>> from jinja2 import Template

>>> template = Template('Hello {{ name }}!')

>>> template.render(name='John Doe')

'Hello John Doe!'

Using template and var file
    ymlvariablefile = ''
    jinja2templatefile = ''

    # the checkargument function, only make sure the arg( file names) have been passed on.
    ymlvariablefile ,jinja2templatefile = checkargument(argv)

    #print("yml:", ymlvariablefile ,"\nj2: ",jinja2templatefile)

    #Load data from YAML into Python dictionary
    config_data = yaml.load(open(ymlvariablefile))

    #Load Jinja2 template from the dirctory called: templates
    j2_env = Environment(loader = FileSystemLoader('./templates'), trim_blocks=True, lstrip_blocks=True)
    template = j2_env.get_template(jinja2templatefile)

    #Render the template with data and print the output
    print(template.render(config_data))

    print("###################################################")
    print("\tyml:", ymlvariablefile, "\n\tj2: ", jinja2templatefile)
    print("La FIN")
render jinja2 : option 1 
from jinja2 import Template

def render_jinja2():
    with open(r"C:\Users\jkriker\Documents\GitHub\JAUT_Training\Basic-python-with-Juniper\Napalm\config_unit.j2") as file_:
        template = Template(file_.read())
    print(template.render(unit_id='5', vlan_id=5, subnet="0.5"))


render_jinja2(template_name, list_variables)

Example using it:

https://github.com/dahai0013/Basic-python-with-Juniper/tree/master/Napalm


option 2 
import jinja2

def render_j2():
    templateLoader = jinja2.FileSystemLoader(searchpath = r"C:\Users\jkriker\Documents\GitHub\JAUT_Training\Basic-python-with-Juniper\Napalm" )
    templateEnv = jinja2.Environment(loader=templateLoader)
    TEMPLATE_FILE = "config_unit.j2"
    template = templateEnv.get_template(TEMPLATE_FILE)
    outputText = template.render(unit_id=5, vlan_id=5, subnet="0.5")
    print(outputText)

Option 3 
from jinja2 import Environment, FileSystemLoader

def render_config(config_template):
    file_loader = FileSystemLoader(r"C:\Users\jkriker\Documents\GitHub\JAUT_Training\Basic-python-with-Juniper\Napalm")
    env = Environment(loader=file_loader)
    template = env.get_template("config_unit.j2")
    output = template.render(unit_id="5", vlan_id="5", subnet="0.5")
    print(output)