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.