Why is there no output in jinja2 Loop?

May 31, 2022

i try to loop over a dic in my jinja template. But i always get no output.

dic={"SERVICE1" : "tess","SERVICE2" : "test"}

with open(Path(Path.cwd()/"test.jinja")) as f:
template = Template(f.read()).render(data_nebula_docker)
print(template)

My template looks like this:

{% for item in dic %}
{{item}}
{% endfor %}

Normal Variablse are working fine. Does i have some basic misunderstanding?
Thx for your help!

>Solution :

There are a couple of problems with your code. I’m going to assume the indentation issue in your with statement is just a copy-and-paste error, and that your code actually looks like:

with open(Path(Path.cwd()/"test.jinja")) as f:
    template = Template(f.read()).render(data_nebula_docker)
    print(template)

In your template you’re referencing a variable dic, but you aren’t passing this to the render method. You want:

from jinja2 import Template
from pathlib import Path

dic = {"SERVICE1": "tess", "SERVICE2": "test"}

with open(Path(Path.cwd() / "test.jinja")) as f:
    template = Template(f.read()).render(dic=dic)
    print(template)

Which produces:


SERVICE1

SERVICE2

You’ll note that this only prints out the keys in your dictionary. When you iterate over a dictionary (in Jinja or Python), you get a list of keys. If you want (key, value) tuples instead, use the .items() method:

{% for item in dic.items() %}
{{item}}
{% endfor %}

Which produces:


('SERVICE1', 'tess')

('SERVICE2', 'test')

Separately, your use of pathlib.Path is a little convoluted; you can write instead:

with (Path.cwd()/"test.jinja").open() as f:

In the above:

It’s not necessary to wrap the result of Path() / "string" in a call to Path() (because it’s already a Path)
A Path object has an open method, so we can call .open() on the Path that results from Path.cwd()/"test.jinja".

Although in this case, your pathlib based code isn’t much of a win over: