10. Prompt Templates

flowchart LR
    subgraph NOTEMPLATES["Without Templates"]
        A["Copy-paste\nprompt 1"] --> B["Modify for\nscenario A"]
        A --> C["Modify for\nscenario B"]
        B --> D["❌ Inconsistent,\nhard to maintain"]
        C --> D
    end

    subgraph TEMPLATES["With Templates"]
        E["Template\n{{variable}}"] --> F["Render with\nscenario A data"]
        E --> G["Render with\nscenario B data"]
        F --> H["✅ Consistent,\neasy to update"]
        G --> H
    end

    style NOTEMPLATES fill:#ef4444,color:#fff
    style TEMPLATES fill:#22c55e,color:#fff

// Without function — repetitive code
function createEmail1() { return `Hello Alice...` }
function createEmail2() { return `Hello Bob...` }

// With function — reusable
function createEmail(name) { return `Hello ${name}...` }

// Without template — repetitive prompts
Prompt 1: "Review this code written by Alice: [code]"
Prompt 2: "Review this code written by Bob: [code]"

// With template — reusable
Template: "Review this code written by {{author}}: {{code}}"

flowchart TD
    TEMPLATE["Prompt Template"] --> FIXED["Fixed Elements\nAlways the same"]
    TEMPLATE --> VARIABLE["Variables\nFilled at runtime"]
    TEMPLATE --> CONDITIONAL["Conditionals\nIncluded based on context"]
    TEMPLATE --> LOOPS["Loops/Repeaters\nFor lists of items"]

    style TEMPLATE fill:#8b5cf6,color:#fff
    style FIXED fill:#3b82f6,color:#fff
    style VARIABLE fill:#f59e0b,color:#fff
    style CONDITIONAL fill:#22c55e,color:#fff
    style LOOPS fill:#ec4899,color:#fff

const template = `You are a {{role}} specializing in {{technology}}.
Review this code written in {{language}}:

{{code}}

Focus on {{focus_area}}. Provide {{num_suggestions}} specific suggestions.`;

const prompt = render(template, {
  role: "senior engineer",
  technology: "React",
  language: "TypeScript",
  code: codeSnippet,
  focus_area: "performance",
  num_suggestions: "3"
});

---
system: You are a {{persona}}
---

Task: {{task}}

Context:
{% if hasContext %}
{{context}}
{% endif %}

{% if examples.length > 0 %}
Examples:
{% for example in examples %}
Input: {{example.input}}
Output: {{example.output}}
{% endfor %}
{% endif %}

User Request: {{userInput}}

prompt_template = """
You are a {role} specializing in {technology}.

Review this code:
{code}

Focus areas: {focus_areas}
Provide exactly {num_suggestions} suggestions.
Return as JSON: {json_schema}
"""

prompt = prompt_template.format(
    role="Senior Engineer",
    technology="Python",
    code=code_snippet,
    focus_areas="performance, readability",
    num_suggestions=3,
    json_schema='{"suggestions": [{"issue": "", "fix": ""}]}'
)

---
You are a {{role}}.

Task: {{task}}
Context: {{context}}

Return your response in the following format:
{{output_format}}
---

---
Classify the intent of each message.

Categories: {{categories}}

Examples:
{% for example in examples %}
Message: {{example.input}}
Intent: {{example.output}}
{% endfor %}

Now classify:
Message: {{new_message}}
Intent:
---

---
Step 1: {{step1_instruction}}
{{step1_input}}

Step 2: Using the output from Step 1, {{step2_instruction}}
{{step1_output}}

Step 3: Finally, {{step3_instruction}}
{{step2_output}}
---

flowchart TD
    SYSTEM["Template Management"] --> STORAGE["Storage\nFiles, DB, Registry"]
    SYSTEM --> VERSIONING["Versioning\nGit, Semantic versions"]
    SYSTEM --> RENDERING["Rendering\nVariable substitution"]
    SYSTEM --> TESTING["Testing\nUnit tests for templates"]
    SYSTEM --> DEPLOYMENT["Deployment\nAPI integration"]

    style SYSTEM fill:#8b5cf6,color:#fff

prompts/
├── code-review/
│   ├── v1.md
│   ├── v2.md
│   └── v3.md
├── data-extraction/
│   ├── invoice.md
│   └── email.md
└── customer-support/
    ├── refund.md
    └── complaint.md

{
  "prompts": {
    "code-review": {
      "template": "You are a {{role}}. Review this {{language}} code...",
      "variables": ["role", "language", "code", "focus"],
      "version": "3.2.1",
      "model": "gpt-4o",
      "created": "2024-01-15",
      "tests": ["test_positive_feedback", "test_critical_issues"]
    }
  }
}

Template: code_review/v2

---
You are a {{role}} with {{years}} years of experience.

Review the following {{language}} code:

```{{language}}
{{code}}

{
  "overall_assessment": "positive|needs_work|critical",
  "issues": [
    {"severity": "", "line": "", "description": "", "fix": ""}
  ],
  "summary": ""
}

Template: support/refund_request

---
You are a {{tier}} customer support agent for {{company}}.

Customer: {{customer_name}}
Account Tier: {{account_tier}}
Issue: {{issue_description}}
Order Value: ${{order_value}}
Days Since Purchase: {{days_since_purchase}}

Company Policy:
{{policy_rules}}

Draft a response that:
1. Acknowledges the customer's frustration
2. Explains what we can do based on policy
3. Offers {{resolution_option}}
4. Sets clear expectations for next steps

Tone: {{tone}}
---

from langchain.prompts import PromptTemplate

template = PromptTemplate(
    input_variables=["topic", "audience"],
    template="""Explain {topic} to a {audience}.
    Use analogies and real-world examples.
    Keep it to 3 paragraphs."""
)

prompt = template.format(topic="Docker", audience="beginner developer")

import { generateText } from 'ai';

const { text } = await generateText({
  model: openai('gpt-4o'),
  system: `You are a ${role} specializing in ${technology}.`,
  prompt: `Review this code:\n\n${code}`,
});