Creating and Testing Programs, Basic Debugging

Lecture 5: Creating and Testing Programs, Basic Debugging

Writing Larger Programs

  • Importance of Planning: As programs grow in size and complexity, meticulous planning before coding becomes crucial.

  • Software Engineering: This computer science subfield focuses on processes for constructing extensive software. While not building large-scale software in this course, fundamental principles of good software construction are applicable.

  • Key Principles: The lecture will cover practical principles for managing program size and complexity.

Commenting

  • Definition: Comments are descriptive textual notes embedded directly into the program's code.

  • Execution: For the most part, comments are not executed by the computer; they are solely for human comprehension.

  • Purpose: Comments aid understanding for:

    • Other developers who read your code.

    • Your future self, when revisiting the code.

    • Maintaining clarity within large, intricate programs.

  • Python Comment Syntax:

    • Use the hash symbol (#) to initiate a comment.

    • Everything following the # on that line is ignored by the Python interpreter.

  • Effective Use of Comments: Comments should be used to:

    • Describe purpose: Explain a line or section of code.

      • Example:
        python # Find the largest factor of x factor = x - 1 while (x % factor) != 0: factor -= 1

    • Define variables: Clarify the role of a particular variable.

      • Example:
        python total = 0 # will hold the total cost of all items sold sum -= odd_sum # sum now holds sum of all even numbers length = dist * sin(angle * pi / 180) # angle is in degrees

    • Clarify computations: Provide context for complex or non-obvious calculations.

      • Example:
        python # Perform first-order simulation with constant acceleration new_state = euler(x0, v0, a, t)

    • Reference external sources: Link to documentation, algorithms, or constants.

      • Example:
        python NA = 6.02214076e23 # Avogadro’s Number # Kruskal’s Algorithm as described in # Corman, Leiserson, Rivest, Stein, “Introduction to # Algorithms” 3rd edition.

    • Separate code sections: Create visual breaks to organize code.

      • Example:
        python ##### Get user input #####

  • Ineffective Use of Comments: Avoid using comments to:

    • Restate obvious code: Don't explain what is self-evident from the code itself.

      • Example of what not to do:
        python numAnimals = 3 # set the number of animals to 3 counter += 1 # increase counter by 1

    • Include irrelevant information: Comments should be pertinent to the code.

      • Exception: Header information (e.g., author, date created, modifications) is a valid, required exception.

        #I am so tired of writing this code (irrelevant)
dist_km = dist_mi * km_per_mi

### taxestimator.py
# Author: Stan Lee
# Date Created: 1/1/2020
# Modified: Jane Doe 2/2/2020

  • **Triple-Quoted Strings as