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Templates

Form Letters with Blanks

Imagine a birthday party invitation:

Dear {{ name }}, you are invited to {{ host }}'s party on {{ date }} at {{ time }}!

You print 20 copies and fill in a different name on each one. The invitation is the template, and the names are the context.

A web template works the same way -- it's HTML with {{ blanks }} that get filled in with real data.

How It Works

from pyweb.template import render

html = render(
    "<h1>Hello, {{ name }}!</h1><p>Your score: {{ score }}</p>",
    {"name": "Alice", "score": 95}
)
# Result: "<h1>Hello, Alice!</h1><p>Your score: 95</p>"

The engine finds every {{ word }} and replaces it with the matching value from the context dictionary.

Using Template Files

Instead of writing HTML in your Python code, you can put it in a file:

templates/greeting.html: 

<html>
<body>
    <h1>Hello, {{ name }}!</h1>
    <p>Welcome to {{ site_name }}.</p>
</body>
</html>

Python code: 

from pyweb.template import render_file

html = render_file("templates/greeting.html", {
    "name": "Alice",
    "site_name": "PyWeb"
})

What Happens to Missing Values?

If a placeholder has no matching key in the context, it stays as-is:

render("Hello, {{ name }}!", {})
# Result: "Hello, {{ name }}!"

This makes it easy to spot mistakes -- you'll see the raw {{ name }} in your page instead of a blank space.

What We Test

  • Single and multiple placeholders are replaced.
  • Missing keys are preserved (not errored).
  • Integer and boolean values are converted to strings.
  • Extra whitespace inside {{ }} is handled.
  • Template files are loaded and rendered.

Next Up

We have all the pieces -- parsing requests, building responses, routing URLs, and rendering templates. Now we need to put them all together. Head to Server.