python jinja - ghdrako/doc_snipets GitHub Wiki

Jinja

Jinja template

contains variables and/or expressions, which get replaced with values when a template is rendered; and tags, which control the logic of the template.

Delimiter:

• {% ... %} for Statements
• {{ ... }} for Expressions to print to the template output
• {# ... #} for Comments not included in the template output
• # ... ## for Line Statements

from jinja2 import Template

Filters

Jinja2 filters allow data manipulation and can be used in conjunction with variables:

{{ some_variable | default('Default Value') }}

The filters in Jinja2 transform variables and can be used for various purposes:

• default: Provides a default value if a variable is undefined.
• length: Returns the length of a string or list.
• to_json: Converts data into JSON format.
• regex_replace: Performs a regular expression replace operation.

Conditionals

Conditional statements like if-else can be used inside templates:

{% if users %}
  {% for user in users %}
    {{ user.name }}
  {% endfor %}
{% else %}
  No users found.
{% endif %}

Loops

You can loop over sequences using the for loop:

{% for item in items %}
  {{ item }}
{% endfor %}

Macros

Macros are reusable snippets of code:

{% macro say_hello(name) %}
  Hello, {{ name }}!
{% endmacro %}

Template Inheritance

You can create a base template and then extend it in child templates. This allows for consistent layouts:

{% extends "base.html" %}
{% block content %}
This content replaces the base content block.
{% endblock %}

name = 'Peter'
age = 34
tm = Template("My name is {{ name }} and I am {{ age }}")
msg = tm.render(name=name, age=age)
print(msg)

Dictionary

person = { 'name': 'Person', 'age': 34 }

tm = Template("My name is {{ per.name }} and I am {{ per.age }}")
# tm = Template("My name is {{ per['name'] }} and I am {{ per['age'] }}")
msg = tm.render(per=person)

print(msg)

Escape special symbols

data = '''
{% raw %}
His name is {{ name }}
{% endraw %}
'''

tm = Template(data)
msg = tm.render(name='Peter')

print(msg)

Jinja for expressions

templates/showpersons.txt:
{% for person in persons -%}
    {{ person.name }} {{ person.age }}
{% endfor %}

from jinja2 import Environment, FileSystemLoader

persons = [
    {'name': 'Andrej', 'age': 34}, 
    {'name': 'Mark', 'age': 17}, 
    {'name': 'Thomas', 'age': 44}, 
    {'name': 'Lucy', 'age': 14}, 
    {'name': 'Robert', 'age': 23}, 
    {'name': 'Dragomir', 'age': 54}
]

file_loader = FileSystemLoader('templates')
env = Environment(loader=file_loader)

template = env.get_template('showpersons.txt')

output = template.render(persons=persons)
print(output)

rainbow.txt:

{% for color in colors %}
    {{ color }}
{% endfor %}

Render with a list of colors.

template = env.get_template('rainbow.txt')

colors = ['red', 'green', 'blue']

output = template.render(colors=colors)
print(output)
```

This is a cheat sheet for the Jinja templating syntax.
Syntax

The syntax is somewhat similar to ERB except for {} instead of <> quotes
```
 {{ ... }}           # Escaping for expressions that create output
 {% ... %}           # Escaping for control statements
 # ... ##            # Line statements
```
Loops
```
 {% for i in list %} ... {% endfor %}
```
Functions

Defining functions
```
 {% macro myfunct(param1, param2) %}
 ...
 {% endmacro %}
```
Using functions
```
 {% myfunc(var, 5) %}
```