#!/usr/bin/python -tt
# Copyright 2010 Google Inc.
# Licensed under the Apache License, Version 2.0
# http://www.apache.org/licenses/LICENSE-2.0

# Google's Python Class
# http://code.google.com/edu/languages/google-python-class/

"""Wordcount exercise
Google's Python class

The main() below is already defined and complete. It calls print_words()
and print_top() functions which you write.

1. For the --count flag, implement a print_words(filename) function that counts
how often each word appears in the text and prints:
word1 count1
word2 count2
...

Print the above list in order sorted by word (python will sort punctuation to
come before letters -- that's fine). Store all the words as lowercase,
so 'The' and 'the' count as the same word.

2. For the --topcount flag, implement a print_top(filename) which is similar
to print_words() but which prints just the top 20 most common words sorted
so the most common word is first, then the next most common, and so on.

Use str.split() (no arguments) to split on all whitespace.

Workflow: don't build the whole program at once. Get it to an intermediate
milestone and print your data structure and sys.exit(0).
When that's working, try for the next milestone.

Optional: define a helper function to avoid code duplication inside
print_words() and print_top().

"""
import sys

def print_words(filename):
  # run helper function to get wordcount list of the input file text
  wordcount = helper(filename)
  # print the list sorted alphabetically by key
  print sorted(wordcount)

def print_top(filename):
  # run helper function to get wordcount list of the input file text  
  wordcount = helper(filename)
  # sort the list by value descending
  wordcount_sorted = sorted(wordcount, key=lambda last_element: last_element[1], reverse=True)
  # print the top 20
  print wordcount_sorted[0:19]

def helper(filename):
  # open the input file
  f = open(filename)
  # read the entire input file into a single string
  text = f.read()
  # use the split() function to split the text on all whitespace to create a word list
  words = sorted(text.lower().split())
  # initialize a dict
  dict = {}
  # iterate through each string in the input string list
  for word in words:
    # check if the word already exists in the dictionary
    if word not in dict:
      # word does not exist - add the word to the dictionary and set it's counter equal to one
      dict[word] = 1
    else:
      # word exists - get the current counter and increment by one
      count = dict[word]+1
      # update the counter for this word
      dict[word] = count
  wordcount = dict.items()
  return wordcount



# Define print_words(filename) and print_top(filename) functions.
# You could write a helper utility function that reads a file
# and builds and returns a word/count dict for it.
# Then print_words() and print_top() can just call the utility function.

###

# This basic command line argument parsing code is provided and
# calls the print_words() and print_top() functions which you must define.
def main():
  if len(sys.argv) != 3:
    print 'usage: ./wordcount.py {--count | --topcount} file'
    sys.exit(1)

  option = sys.argv[1]
  filename = sys.argv[2]
  if option == '--count':
    print_words(filename)
  elif option == '--topcount':
    print_top(filename)
  else:
    print 'unknown option: ' + option
    sys.exit(1)

if __name__ == '__main__':
  main()