Lab: Prompt Templates

Build type-safe prompt templates with variable substitution.

Objectives

• Create reusable templates
• Implement variable validation
• Build a prompt library

Demo Code

See demos/course4/week2/prompt-engineering/

Lab Exercise

See labs/course4/week2/lab_2_6_prompt_templates.py

Key Implementation

#![allow(unused)]
fn main() {
pub struct PromptTemplate {
    template: String,
    variables: Vec<String>,
}

impl PromptTemplate {
    pub fn render(&self, vars: &HashMap<String, String>) -> Result<String, PromptError> {
        let mut result = self.template.clone();
        for var in &self.variables {
            let value = vars.get(var)
                .ok_or(PromptError::MissingVariable(var.clone()))?;
            result = result.replace(&format!("{{{}}}", var), value);
        }
        Ok(result)
    }
}
}