Outline for October 20, 2025

Reading: §4.5, 7, 9
Assignments: Homework 2, due October 29, 2025

1. Greetings and Felicitations!
   1. Thursday’s office hours moved to 12:10pm–1:00pm (they are in person)

2. Printing [printing.py]

3. Recursion
   1. Tower of Hanoi [hanoi.py]

4. Using random numbers
   1. import random
   2. Problem: compute π by tossing darts at a unit square
   3. First build routine to simulate dart toss at unit square [mc-1.py]
   4. Then build routine to see if co-ordinates are in unit circle [mc-2.py]
   5. Then build routine to read in number of tosses [mc-3.py]
   6. Put it all together [mc-4.py]
   7. Graphics! [mc-5.py]

5. Files
   1. What is a file?
   2. What can you do with it? (For example, read, write, append)
   3. Types of files (text, binary)

6. File Input and Output for text files
   1. Opening and closing: open(filename, mode), close()
   2. Reading: readline(), readlines(), read(), read(n)
   3. Writing: write(str), writelines(list)

7. Exception EOFError — input function encounters an end of file

8. Examples
   1. Print out a named file [fileio1.py]
   2. Print out a named file and prepend line numbers [fileio2.py]
   3. Store the output in filename.lst [fileio3.py]

9. Examples
   1. Put lines in a file in random order [randlines.py]
   2. Read in a list of words from a file, then search it as requested; similar to linear search program [search-1.py]
   3. Now see how many words you checked total [search-1c.py]

10. Dictionary
    1. Collection of key-value pairs

11. Creating dictionaries
    1. Using d = {}
    2. Using d = dict()

12. Methods for dictionaries
    1. k in D: True if dictionary D has key k; else False
    2. D.keys(): list of keys in D
    3. D.values(): list of values in D
    4. D.items(): list of tuples (key, value) in D
    5. D.get(k, d): if key k in D, return associated value; else return d
    6. del D[k]: delete tuple with key k from D
    7. D.clear(): delete all entries in D

13. Example: memos
    1. Remember how slowly the recursive Fibonacci number program rfib.py ran? Here is a faster recursive version that uses memos [rfibmemo.py]

14. Example: word frequency count
    1. Unsorted [wfc-1.py]
    2. Sorted alphabetically [wfc-2.py]
    3. Sorted alphabetically, but dictionary order (note key=str.lower() in sorted [wfc-3.py]
    4. Sorted by frequency (treat lambda x: x[1] as an idiom to reference the value of the dictionary entry, not the key—to go from highest to lowest, replace x[1] with -x[1]) [wfc-4.py]
    5. Sorted by frequency first, then alphabetically—note use of function alphafreq(x); you can use any function here, and the parameter is the item [wfc-5.py]

15. Handling exceptions
    1. except [except0.py]
    2. except exceptcode [except1.py]
    3. else [except2.py]
    4. except exceptcode as msgvar [except3.py]
    5. finally [except4.py]
    6. Exceptions in a function: who handles them? [except5.py, except6.py]
    7. Using global variables as error flags [except7.py]
    8. raise exceptcode message [except8.py]

Matt Bishop Office: 2209 Watershed Sciences Phone: +1 (530) 752-8060 Email: mabishop@ucdavis.edu

MHI 289I, Programming in Health Informatics Version of October 24, 2025 at 10:43PM

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