Lab Cycle 3 — File Handling & Exception Handling

def copy_alternate_odd_lines(source_file, dest_file):
    """
    Reads source_file and copies only odd-numbered lines (1, 3, 5, ...)
    to dest_file using context managers.
    """
    copied_count = 0
    try:
        with open(source_file, 'r') as fin, open(dest_file, 'w') as fout:
            for line_number, line in enumerate(fin, start=1):
                if line_number % 2 != 0:  # Odd numbered line
                    fout.write(line)
                    copied_count += 1
                    
        print(f"Successfully copied {copied_count} odd-numbered lines to '{dest_file}'.")
    except FileNotFoundError:
        print(f"Error: Source file '{source_file}' not found!")
    except Exception as e:
        print(f"An unexpected error occurred: {e}")

def create_sample_file(filename):
    with open(filename, 'w') as f:
        f.write("Line 1: Python programming basics\n")
        f.write("Line 2: Data Structures and Algorithms\n")
        f.write("Line 3: Database Management Systems\n")
        f.write("Line 4: Computer Networks\n")
        f.write("Line 5: Artificial Intelligence\n")
        f.write("Line 6: Operating Systems\n")

def main():
    src = "file1.txt"
    dest = "file2.txt"
    
    # Create sample file for demonstration
    create_sample_file(src)
    
    # Execute copy function
    copy_alternate_odd_lines(src, dest)
    
    # Display destination file contents
    print("\n--- Contents of file2.txt (Odd Lines) ---")
    with open(dest, 'r') as f:
        print(f.read(), end="")

if __name__ == "__main__":
    main()