55 mins lesson duration•10 mins read

Lesson 23: Prompting for Code Generation

The CODE framework, before/after examples, and the mistakes that make AI write broken code.

Why Code Prompts Are Different

Code must be correct, not just plausible. Vague prompts produce confident-looking but broken code. The fix: give the model the contract — inputs, outputs, constraints, and examples.

The CODE Framework

Letter	Element	What You Provide
C	Context	What is this for? What are the inputs?
O	Output	Function signature, return type, docstring
D	Dependencies	Libraries allowed/forbidden, versions
E	Examples	Input → expected output pairs

Bad vs. Good Code Prompt

Bad:

Write a function to calculate the average of a list.

→ Ambiguous: what about empty lists? floats? rounding?

Good:

Write a Python function that computes the average of a list of numbers.

CONTEXT:
- Input: a list of floats, e.g. [10, 20, 30]
- Handle empty lists (return None)

OUTPUT:
- A function named average(values)
- Include a docstring and one usage example

DEPENDENCIES:
- Standard library only

EXAMPLE:
average([10, 20, 30]) -> 20.0

Edge Cases to Always Specify

Empty input, single item, negative numbers, zero division.
What to return on failure (None, error, exception?).
Performance constraints (large inputs?).
Mutating the input vs. returning a copy.

Ask for Tests, Then Verify

The professional workflow:

1. "Write the function per the spec."
2. "Now write 5 test cases including edge cases."
3. "Run the tests and fix any failures."

Never trust generated code blindly — run it, review it, and test edge cases yourself. AI code can be subtly wrong (off-by-one, wrong library API, security holes).

Common Code Prompt Mistakes

Mistake	Fix
No signature/return spec	Define the exact interface
No example	Show input → output
No constraints	State allowed libraries and limits
No edge cases	Ask for edge-case handling explicitly
No tests	Chain a test-generation step

Example: Refactor Request

Refactor this function to be faster and easier to test:
[code]

Keep the same public interface (same name, params, return).
Use only the standard library. Add a short comment explaining
the new approach.

Key Takeaways

Code prompts need a contract: context, output, dependencies, examples (CODE).
Specify edge cases explicitly and ask for tests.
Verify generated code by running it — never trust it blindly.
Keep the public interface stable when asking for refactors.

Next up: Prompting for writing and content — tone, audience, and the WRITE framework.

Interactive Lesson Code Snippet

# The CODE framework: Context, Output, Dependencies, Examples
prompt = """Write a Python function that computes the average of a list of numbers.

CONTEXT:
- Input: a list of floats, e.g. [10, 20, 30]
- Handle empty lists (return None)

OUTPUT:
- A function named average(values)
- Include a docstring and one usage example

DEPENDENCIES:
- Standard library only

EXAMPLE:
average([10, 20, 30]) -> 20.0
"""

print(prompt)

# The generated code - verify it actually works
def average(values):
    """Return the mean of a list of numbers, or None if empty."""
    if not values:
        return None
    return sum(values) / len(values)

print("Result:", average([10, 20, 30]))
print("Empty list:", average([]))

Language: python

Lesson Code (Python)

# The CODE framework: Context, Output, Dependencies, Examples
prompt = """Write a Python function that computes the average of a list of numbers.

CONTEXT:
- Input: a list of floats, e.g. [10, 20, 30]
- Handle empty lists (return None)

OUTPUT:
- A function named average(values)
- Include a docstring and one usage example

DEPENDENCIES:
- Standard library only

EXAMPLE:
average([10, 20, 30]) -> 20.0
"""

print(prompt)

# The generated code - verify it actually works
def average(values):
    """Return the mean of a list of numbers, or None if empty."""
    if not values:
        return None
    return sum(values) / len(values)

print("Result:", average([10, 20, 30]))
print("Empty list:", average([]))

Console Output

Write a Python function that computes the average of a list of numbers.

CONTEXT:
- Input: a list of floats, e.g. [10, 20, 30]
- Handle empty lists (return None)

OUTPUT:
- A function named average(values)
- Include a docstring and one usage example

DEPENDENCIES:
- Standard library only

EXAMPLE:
average([10, 20, 30]) -> 20.0

Result: 20.0
Empty list: None

Code Visualization Tips

Draw the CODE framework as a 4-box spec sheet the model must fill in.
Show bad vs. good code prompts side by side, annotating what each added line fixes.
Sketch the verify loop: generate → test → fix → re-test until green.

Professional Tips & Tricks

Include one runnable example pair — models infer intent from examples better than prose.
Ask for tests FIRST, then code — the tests act as a spec.
For refactors, paste the current interface and forbid changing it.

Python Code Judge & Practice Arena

LeetCode Style

Run real Python 3.12 WebAssembly code directly in your browser against automated test suites.

Solved:0 / 1

0 / 20 XP

Challenges:

Problem 1 of 1

Write a CODE Prompt

Medium+20 XP

Write a CODE-framework prompt for a function that counts word frequency in a string, including edge cases (punctuation, case) and one example.

main.pyPython 3.12 (WASM)

# Write a CODE Prompt
# Write your solution below

def solve():
    pass

Press Run Code to test or Submit to verify test cases

Test Your Knowledge

Instant feedback

Quick Check: Prompting for Code

1 / 2

What does the CODE framework stand for?

Up next · Continue learning

Prompting for Writing & Content

The WRITE framework for audience, tone, and format — with before/after examples for posts, emails, and articles.

10 mins read50 mins

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