Prompt Templates with Variables

Example

A wrapper that fails loudly when a variable is missing (a silent empty slot gives the model a broken prompt):

from string import Template

REPLY = Template("""You are ShopEase support.
Customer name: $name
Order: $order_id ($status)

<policy>
$policy
</policy>

Reply in JSON like {"reply": "...", "escalate": false}.
Customer message: $message""")

def render(template, **values):
    needed = {m.group("named") or m.group("braced")
              for m in template.pattern.finditer(template.template)
              if m.group("named") or m.group("braced")}
    missing = sorted(needed - values.keys())
    if missing:
        raise KeyError(f"missing template variables: {missing}")
    return template.substitute(**values)

print(render(REPLY, name="Ravi", order_id="SE-30112", status="shipped",
             policy="Orders can be cancelled until they are shipped.",
             message="Cancel my order please"))
try:
    render(REPLY, name="Ravi", message="hi")
except KeyError as e:
    print("\nerror:", e)

Output

You are ShopEase support.
Customer name: Ravi
Order: SE-30112 (shipped)

<policy>
Orders can be cancelled until they are shipped.
</policy>

Reply in JSON like {"reply": "...", "escalate": false}.
Customer message: Cancel my order please

error: "missing template variables: ['order_id', 'policy', 'status']"