Challenge 3 the tribonacci sequence

[AnaiMurillo]

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name: Challenge: The Tribonacci Sequence
about: A template PR for code review with a checklist

Behavior

The "Tribonacci sequence" challenge is a twist on the famous Fibonacci sequence, where each number is the sum of the preceding three numbers.

For example, 0, 1, 1, 2, 4, 7 …

Write a function that returns the nth number in the Tribonacci sequence.

Example

tribonacci(5)
# Output: 4 (0, 1, 1, 2, 4)

tribonacci(7)
# Output: 13 (0, 1, 1, 2, 4, 7, 13)

Files

• The file name describes the function's behavior
• There is a module docstring in the function file
• The test file's name matches the function file name -
  /tests/test_file_name.py
• There is a module docstring in the tests file

Unit Tests

• The test class has a helpful name in PascalCase
• The test class has a docstring
• Every unit test has
  • A helpful name
  • A clear docstring
  • Only one assertion
  • There is no logic in the unit test
• All tests pass
• There are tests for defensive assertions
• There are tests for boundary cases

Function Docstring

• The function's behavior is described
• The function's arguments are described:
  • Type
  • Purpose
  • Other assumptions (eg. if it's a number, what's the expected range?)
• The return value is described
  • Type
  • Other assumptions are documented
• The defensive assertions are documented using Raises:
  • Each assumption about an argument is checked with an assertion
  • Each assertion checks for only one assumption about the argument
• Include 3 or more (passing!) doctests

The Function

• The function's name describes it's behavior
• The function's name matches the file name
• The function has correct type annotations
• The function is not called in the function file

Strategy

Do's

• Variable names help to understand the strategy
• Any comments are clear and describe the strategy
• Lines of code are spaced to help show different stages of the strategy

Don'ts

• The function's strategy is not described in the documentation
• Comments explain the strategy, not the implementation
• The function does not have more comments than code
  • If it does, consider finding a new strategy or a simpler implementation

Implementation

• The code passes the formatting checks
• The code passes all Ruff linting checks
• The code has no (reasonable) Pylint errors
  • In code review, you can decide when fixing a Pylint error is helpful and
    when it's too restricting.
• Variables are named with snake_case
• Variable names are clear and helpful
• The code follows the strategy as simply as possible
• The implementation is as simple as possible given the strategy
• There are no commented lines of code
• There are no print statements anywhere
• The code includes defensive assertions
• Defensive assertions include as little logic as possible

[likechrisss]

Great work but some things are missing for it to be perfect :

1. You forgot the READMe file
2. The Function's Strategy Is Not Described in the Documentation (The current docstring briefly explains the Tribonacci sequence but doesn’t describe the iterative approach used in the function.)
3. It also lacks comments that explicitly describe the iterative approach used to compute the Tribonacci sequence.

[AnaiMurillo]

@likechrisss
I have already made the requested changes, thanks for your recommendations!!! I will keep an eye out in case something is missing.

[likechrisss]

Everything is now perfect.
Excellent job.