[Python] Python/Jinja — Having difficulty outputting a for loop of posts into a template

I'm migrating my website over to Python and Jinja (no frameworks, I wanted to make my own modules and scripts and learn Python better in the process), and I'm using this Real Python tutorial for making a for loop and outputting the data to a template: https://realpython.com/primer-on-jinja-templating/#leverage-for-loops

I've adapted the write_messages.py code to work with my existing template for my posts and the data, so the template HTML looks like this:

{% for post in posts %}
<article>
<h2><a class="permalink" href="/">{{ title }}</a></h2>
<p>{{ body }}</p>
<time>{{ date }}</time>
<p class="tag">Tags: <a class="tags" href="/tags/{{ tags }}">{{ tags }}</a></p>
<hr class="solid">
</article>
{% endfor %}


And the Python script, which I'm calling write-posts.py, looks like this:

# write-posts.py
from jinja2 import Environment, FileSystemLoader
from datetime import datetime, timezone

title = "First Post"
slug = "first-post"
date = 2025-7-6
body = "Hello world!"
tags = "First Post", "Second Tag"
posts = [
{"title": "First Post",},
]

environment = Environment(loader=FileSystemLoader("templates"))
template = environment.get_template("index.html")
filename = "testindex.html"

for post in posts:
content = template.render(
post,
title=title,
slug=slug,
date=date,
body=body,
tags=tags
)
with open(filename, mode="w", encoding="utf-8") as message:
message.write(content)
print(f"... wrote {filename}")


Lines 5-11 in write-posts.py are giving me problems: 1) Using those lines as-is, the testindex.html file generates, but does not output the HTML code for the <article> section. If I remove lines 5-9 and leave the posts dictionary in there, then the terminal tells me NameError: name 'title' is not defined. Did you mean: 'tuple'? (I know I don't need both sets of data in here, I was just trying to figure out how to resolve the NameError and left the code in.)

I've looked over the tutorial's code and mine several times and can't figure out what I'm doing wrong. Any ideas?

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