Notes on Python

Chapter 1: Preparation

This lecture mainly covers lab00, which guides you through setting up your Python environment configuration.

1.Software Setup

1. Terminal:

   Windows comes with Powershell, and I have installed Git Bash.

2. Python:

   Python 3.11 is recommended for this course. However the Microsoft Store only provides versions 3.12 and 3.13 now. So I installed versions 3.12.(Note: The Microsoft Store version installs automatically to a protected directory, which may cause path issues later. Consider downloading the installer from python.org for more control.)

   Verrification:

   test@▒ѩ▒ MINGW64 /e/Computer Science System Building/CS61A/lab
   $ python3 --version
   Python 3.12.10

3. Text Editor:

   The Python interpreter is used to run Python code, but we need a text editor to write Python code.

   VS Code is recommended for this course (thought I initially expected Pycharm would be suggested…).

   Download Link

   Note: Disable Copilot! Press Ctrl+Shift+X to open the Extensions panel and search for GitHub Copilot -> click the gear -> disable feature.

2. Personalizing Your Terminal

VS Code -> Manage(gear icon in the bottom-left corner) -> Settings -> Features -> Terminal

• [x] Enable “Integrated: Copy On Selection”
• [x] Enable “Integrated: Cursor Blinking”
• Set “Integrated: Cursor Style” to “line”
• Set “Terminal › Integrated › Default Profile: Windows” to “Git Bash”

3. Implementation of lab00

1. finish the code

   def twenty_twenty_six():
       """Come up with the most creative expression that evaluates to 2026
       using only numbers and the +, *, and - operators (or ** and % if you'd like).
   
       >>> twenty_twenty_six()
       2026
       """
       return 2*1000+2*10+6

2. test the code locally

   test@□□ѩ□□□□ MINGW64 /e/Computer Science System Building/CS61A/lab/lab00
   $ python3 -m doctest -v lab00.py
   Trying:
       twenty_twenty_six()
   Expecting:
       2026
   ok
   1 items had no tests:
       lab00
   1 items passed all tests:
      1 tests in lab00.twenty_twenty_six
   1 tests in 2 items.
   1 passed and 0 failed.
   Test passed.

3. test by the ok program

   test@□□ѩ□□□□ MINGW64 /e/Computer Science System Building/CS61A/lab/lab00
   $ python3 ok
   =====================================================================
   Assignment: Lab 0
   OK, version v1.18.1
   =====================================================================
   
   Performing authentication
   Please enter your school email (.edu):*****
   Successfully logged in as wye18280075427@gmail.com
   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   Running tests
   
   
   There are still locked tests! Use the -u option to unlock them
   ---------------------------------------------------------------------
   Test summary
       Locked: 1
       1 test cases passed! No cases failed.
   
   Backup... 100% complete
   Backup past deadline by 111 days, 6 hours, 8 minutes, and 5 seconds
   Backup successful for user: wye18280075427@gmail.com
   URL: https://okpy.org/cal/cs61a/sp26/lab00/backups/62QYM7
   
   OK is up to date

4. Key Takeaways

1. Understanding the command python3 -m doctest -v lab00.py ?

python3 invokes the Python 3 interpreter

-m Tells Python to run a module as a script

doctest The built-in module for testing docstrings

-v Short for --verbose, outputs detailed test results

Chapter 2: Building Abstractions with Functions

1. Names

Expressions representing numbers may be combined with mathematical operators to form a compound expression, which the interpreter will evaluate:

>>> 42
42
>>> -1 - -1
0
>>> 1/2 + 1/4 + 1/8 + 1/16 + 1/32 + 1/64 + 1/128
0.9921875

These mathematical expressions use infix notation, where the operator (e.g., +, -, *, or /) appears in between the operands (numbers).