Nov 19: Recursive Walk, Redo Quiz5

Learning Objectives

After today's class, you should be able to:

• Explain how the organization of a file system is recursive.
• Describe a recursive function that traverses a file system.

File System Review

[5 min]

• Folders contain files and other folders, which contain files and other folders, which …
  • An everyday example of recursion!
• Two kinds of paths
  • An "absolute" path (from root of the file system) begins with a slash
  • A "relative" path (from the current folder) does not begin with a slash

Example

• Absolute path to CS149 folder: /home/mayfiecs/CS149 (begins with a slash)
• Relative path to selected file: Homework/HW5/scores.py (does not begin with a slash)
• Absolute path to selected file: /home/mayfiecs/CS149/Homework/HW5/scores.py

Using os and os.path

[5 min]

os – Miscellaneous operating system interfaces

• os.getcwd() – get current working directory
• os.listdir() – get list of directory entries

os.path – Common pathname manipulations

• os.path.isfile(path) – True if regular file
• os.path.basename(path) – get name of the file
• os.path.join(path, path2) – combine two paths

Example: print_files

[15 min]

A recursive function that "walks" the file system: filesys1.py

Sample output when run on my PA1 folder:

PA1:
    .pytest_cache:
        .gitignore
        CACHEDIR.TAG
        README.md
        v:
            cache:
                lastfailed
                nodeids
    __pycache__:
        analysis.cpython-312.pyc
        simplify.cpython-312.pyc
        test_analysis.cpython-312-pytest-8.4.2.pyc
        test_simplify.cpython-312-pytest-8.4.2.pyc
    analysis.py
    main.py
    simplify.py
    test_analysis.py
    test_simplify.py

Quiz 5 Coding Redo

[20 min]

• Log in as student
• Start the recording
• Log in to Gradescope
• You must use Thonny (not VS Code)
• Do not turn off recording; just log out