How to load jinja template directly from filesystem

Question

Here's how: use a FileSystemLoader instead of a PackageLoader. I found examples on the web here and here. Let's say you have a python file in the same dir as your template:

./index.py
./template.html

This index.py will find the template and render it:

#!/usr/bin/python
import jinja2

templateLoader = jinja2.FileSystemLoader(searchpath="./")
templateEnv = jinja2.Environment(loader=templateLoader)
TEMPLATE_FILE = "template.html"
template = templateEnv.get_template(TEMPLATE_FILE)
outputText = template.render()  # this is where to put args to the template renderer

print(outputText)

It turns out, the jinja2 API doc does have a section which discusses all the built-in loaders, so it's kind of embarrassing not to have noticed that right away. But the introduction is worded such that PackageLoader seems to be the default, "simplest" method. For newcomers to python, this can lead to a wild goose chase.

A simpler way is to directly call the jinj2.Template constructor and use open to load the file:

from jinja2 import Template
with open('template.html.jinja2') as file_:
    template = Template(file_.read())
template.render(name='John')

Here is the one liner:

from jinja2 import Template

with open('template_file.j2') as f:
    template = Template(f.read())

Then you can render the template on another line, or for all in one line:

with open('template_file.j2') as f:
    rendered = Template(f.read()).render(var="TEXT")

If using Python 3.4+ and Jinja2 - v2.11+ -- we can combine python's pathlib and Filesystem to simplify the flow

from pathlib import Path
...

p = Path(__file__).parent.parent / 'templates' # sample relative path
env = Environment(
    loader=FileSystemLoader(Path(p)))
template = env.get_template('your_file.jinja2')

I am not comfortable with using directly Template(file) since Jinja's template inheritance processing may not work well.

Pathlib support is only added in latest version of Jinja - v2.11+