Weekend Info

Exercise05

Exercise 05: Files, Creative uses of lists
==========================================

Introduction
------------
Files can be opened using the .open method, and then processed one character at a time as a bytestream using the .read method with an argument of 1:

    f = open("myfile.txt")
    firstletter = f.read(1)
    f.close()

The entire file can be read in all at once using the .read method with no arguments:

    f = open("myfile.txt")
    filetext = f.read()
    f.close()

Once a file has been read, it can be iterated through as if it were a list:

    # Print one character at a time to the screen
    for char in filetext:
        print char

Resources:
    * http://learnpythonthehardway.org/book/ex15.html
    * http://learnpythonthehardway.org/book/ex16.html
    * http://learnpythonthehardway.org/book/ex17.html
    * http://www.asciitable.com/
    * http://docs.python.org/library/functions.html#ord

Problem Description
-------------------
Write a program, lettercount.py, that opens a file named on the command line and counts how many times each letter occurs in that file. Your program should then print those counts to the screen, in alphabetical order. For example:

    inputfile.txt:
    An abacus

    $ python lettercount.py inputfile.txt
    3
    1
    1
    0
    0
    ...

Once you've produced appropriate output, you can visualize it by piping the contents of your program to the 'spark' utility installed on your computer:

    $ python lettercount.py inputfile.txt | spark
    ▃▂▄▁▇▅█▁▇▂▁▁▅▃▅▇▁▄▄▂▂▇▆▄▂▄

You may find the following two methods useful:
    string.lower()
    ord()

We have provided a file 'twain.txt' for you to test your code on.

Exercise06

Exercise 6: Files and dicts
============================

Introduction
------------
Files can also be iterated line-by-line, using a for loop on the file directly.

For example:
    twain = open('twain.txt')
    for line in twain:

        # Do something

The loop variable 'line' will store each line of the file in turn.

Dictionaries can also be iterated entry-by-entry, using the method iteritems().

For example:
    my_dict = {'a': 1, 'b': 2, 'c': 3}
    for key, value in my_dict.iteritems():
        print "Key == %r, value == %r" % (key, value)

Prints:
Key == 'a', value == 1
Key == 'b', value == 2
Key == 'c', value == 3

This introduces two loop variables, 'key' and 'value', that will store the key
and value elements of each dictionary entry in turn.

Resources:
    * http://learnpythonthehardway.org/book/ex39.html
    * http://www.learnpython.org/page/Dictionaries
    * http://docs.python.org/library/stdtypes.html#string-methods
    * http://docs.python.org/library/stdtypes.html#mapping-types-dict

Problem Description
-------------------

Write a program, wordcount.py, that opens a file named on the command
line and counts how many times each space-separated word occurs in
that file. Your program should then print those counts to the
screen. For example:

    inputfile.txt:
    As I was going to St. Ives
    I met a man with seven wives
    Every wife had seven sacks
    Every sack had seven cats
    Every cat had seven kits
    Kits, cats, sacks, wives.
    How many were going to St. Ives?

    $ python wordcount.py inputfile.txt
    seven 4
    Kits, 1
    sack 1
    As 1
    kits 1
    Ives? 1
    How 1
    St. 2
    had 3
    sacks, 1
    to 2
    going 2
    was 1
    cats, 1
    wives 1
    met 1
    Every 3
    with 1
    man 1
    a 1
    wife 1
    I 2
    many 1
    cat 1
    Ives 1
    sacks 1
    wives. 1
    were 1
    cats 1

You may find the following methods useful:
    string.split()
    string.strip()
    dict.setdefault()
    dict.iteritems()

We have provided a file 'twain.txt' for you to test your code on.

Extra Credit

The output of your program is not as nice as it could be. Try to improve it:

    * Some words are counted separately due to punctuation. Remove punctuation
      so that they appear as the same word in the output.

    * In the example above, 'Kits' and 'kits' are treated separately because they
      have different capitalization. Make all words lowercase so that
      capitalization doesn't matter.

    * Sort the output from the highest frequency words to the lowest frequency
      words.

    * Sort words having the same frequency alphabetically.

Exercise07

Exercise 07: Files and dictionaries
=======

Introduction
--------
Imagine a list as being a numbered sequence of data.

    fish = ["shark", "ray", "halibut", "tuna", "squid"]

The first element is shark, and you access it by its index number:
    print fish[0]
        => shark

To access the nth element, its index number is n-1. The fifth element is accessed thusly:
    print fish[4]
        => squid

What if, instead of a numbered index, we could use a string as an index?
    print fish["deep ocean"]
        => anglerfish
    print fish["shallow river"]
        => candiru

We would then need another way of specifying a list where each element is named.
    fish = {"deep ocean": "anglerfish", "amazon river": "candiru",
            "lake": "bass", "shallow river": "trout"}

This is called a dictionary in python. It's also called a hashtable, or a hashmap, or very non-specifically, a map. A dictionary is a collection of 'key-value pairs'. The key 'deep ocean' _maps_ to the value 'anglerfish'.

Imagine you were writing a program to keep track of user scores in a game. If you only had arrays, you might do something like this:

    names  = ["Bob", "Joe", "Jack", "Jane"]
    scores = [   10,     3,      6,     15]

To find Joe's score, first you'd have to find which position "Joe" is in, then use that position to look up his score.
    index_joe = names.index("Joe")
    print "Joe's score is %d"%(scores[index_joe])
        => Joe's score is 3

This is unwieldy and complicated. With dictionaries, we could instead do the following:
    scores = {"Bob": 10, "Joe": 3, "Jack": 6, "Jane": 15}

    print "Joe's score is %d"%(scores['Joe'])
        => Joe's score is 3 

Dictionaries have a method called 'get' which allows you to have a default value in case a key does not exist beforehand.

    scores = {"Bob": 10, "Joe": 3, "Jack": 6, "Jane": 15}
    print scores.get("Bob", 0) # The second argument is the fallback number if the key doesn't exist
        => 10

    print scores.get("Billy", 0) # Billy doesn't exist in the dictionary, so return the fallback instead
        => 0

Resources:
    * http://learnpythonthehardway.org/book/ex15.html
    * http://learnpythonthehardway.org/book/ex16.html
    * http://learnpythonthehardway.org/book/ex17.html
    * http://docs.python.org/tutorial/inputoutput.html#methods-of-file-objects
    * http://learnpythonthehardway.org/book/ex39.html
    * http://docs.python.org/tutorial/datastructures.html#dictionaries
    * http://stackoverflow.com/a/3437070


Description
-------
In this directory, you will find a text file, scores.txt, containing a series of local restaurant ratings. Each line looks like this:
    
    Restaurant Name:Rating

Your job is to write a program named 'sorted_data.py' reads the file, then spits out the ratings in alphabetical order by restaurant

Sample output:
    Meringue:Exercise07 chriszf$ python sorted_data.py 
    Restaurant 'Andalu' is rated at 3.
    Restaurant "Arinell's" is rated at 4.
    Restaurant 'Bay Blend Coffee and Tea' is rated at 3.
    Restaurant 'Casa Thai' is rated at 2.
    Restaurant 'Charanga' is rated at 3.
    Restaurant 'El Toro' is rated at 5.
    Restaurant 'Giordano Bros' is rated at 2.
    Restaurant "Irma's Pampanga" is rated at 5.
    Restaurant 'Little Baobab' is rated at 1.
    Restaurant 'Pancho Villa' is rated at 3.
    Restaurant 'Taqueria Cancun' is rated at 2.
    Restaurant 'Urbun Burger' is rated at 1.

Week 1 Project

Project 1: Looping, file manipulation, panic
=======

Introduction
-------
This exercise is difficult and should take several days. 

Resources:
    * http://learnpythonthehardway.org/book/ex32.html
    * http://learnpythonthehardway.org/book/ex34.html
    * http://www.learnpython.org/page/Lists
    * http://www.learnpython.org/page/Loops
    * http://www.learnpython.org/page/Basic%20String%20Operations
    * http://docs.python.org/library/os.html#os.listdir
    * http://docs.python.org/library/os.html#os.chdir
    * http://docs.python.org/library/os.path.html#os.path.exists
    * http://docs.python.org/library/shutil.html#shutil.move

Concepts required:
    * for loops
    * conditionals
    * lists
    * paths
    * substrings

Description
-------
Included in the exercise is a zipfile, 'files.zip'. It contains 200 files with random character strings for names, all lowercase. First, unzip this file into a directory named 'original_files'.

Your job is to write a program, ex1.py, that does the following things:

1. Create 26 directories in the current directory, one for each letter of the alphabet:
    ./a/
    ./b/
    ./c/
    etc.

2. Loop through all the files in the original_files directory, and organize each of those files into the directory that their name starts with.

### Example:
    The file named 'artichoke.txt' would go into the directory 'a',
    'bartholomew.txt' would go into 'b'.