Outline for October 26, 2023

Reading: §7
Due: Homework 2, due October 26, 2023

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

2. 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)

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

4. 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]

5. 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]

6. Dictionary
   1. Collection of key-value pairs

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

8. 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

9. 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]

Matt Bishop Office: 2209 Watershed Sciences Phone: +1 (530) 752-8060 Email: [email protected]

ECS 235A, Computer and Information Security Version of October 25, 2023 at 10:08PM

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