Lecture 03/04: CSC1302

Python Programming Overview

• Discussion revolves around writing and executing Python scripts.

• Common IDEs:

  • PyCharm

  • Visual Studio Code

  • Command Line Interface (CLI)

Running Python Scripts

• Typical execution: Write code and run from the UI.

• Not all computers have a GUI (e.g., servers).

• Command Line Arguments: Alternative input method for Python scripts.

Command Line Execution

• Example: Execute a Python script from the command line.

  • Navigate to the directory containing the script:

    • Command: cd /path/to/directory

  • Run script: python test.py

Command Line Arguments

• Provide additional parameters when running scripts.

• Example of running a script with arguments:

  • Command: python script.py arg1 arg2

  • Accessing the arguments in the script via:

    • import sys

    • Use sys.argv, where:

      • sys.argv[0]: script name

      • sys.argv[1]: first argument

      • sys.argv[2]: second argument

Using sys.argv

• Arguments are stored as strings, requiring conversion for mathematical operations.

• Example usage:

  distance = int(sys.argv[1])
  time = int(sys.argv[2])
  speed = distance / time
  print(speed)

Benefits of Command Line Arguments

• Flexible input without a GUI.

• Automation and testing advantages.

Writing a Python Program

• Task: Create a program that counts lines in a text file.

• Usage:

  • Command: python script.py example.txt

  • Inside the script, access the text file via sys.argv[1].

  • Open the file and count lines using:

    with open(filename, 'r') as f:
        lines = f.readlines()
        print(len(lines))

File Types

• Differences between text files and CSV (Comma Separated Values) files.

• CSV files:

  • Read/write using csv module in Python:

    • csv.reader for reading CSV files.

    • csv.writer for writing to CSV files.

Data Structures Overview

• Introduction to data structures with focus on trees.

Trees as Hierarchical Data Structures

• Tree Definition:

  • Root: Topmost node (only one)

  • Branches: Connect nodes in a hierarchy

  • Leaves: Nodes without children

Components of Trees

• Root, children, parent nodes, leaf nodes, and edges.

• Height of a Tree: Number of edges from root to the farthest leaf.

Types of Trees

• General Tree: Nodes can have any number of children.

• Binary Tree: Each node has at most two children.

Classifying Binary Trees

• Full Binary Tree: Every node has either zero or two children.

• Complete Binary Tree: All levels filled except possibly the last, aligned to the left.

• Balanced Binary Tree: The height difference between left and right subtrees is at most one.

Example Problems

• Homework: Identify types of binary trees based on given structures.

Implementing Trees in Python

• Binary trees can be represented using arrays.

  • Array Representation: Root at index 0.

  • Left child at 2i + 1 and right child at 2i + 2.

• Array Binary Tree Class:

  • Structure includes methods for setting child nodes and accessing tree data via indices.