Pythonlearn-exercises-chapter10.py

# Standard Opening - open and read target input text file.
file = raw_input('Enter file name: ')
if len(file) < 1 : file = 'mbox-short.txt'
try :
    fhand = open(file)
except :
    print 'Cannot open file: ', file, '.', '...please try, again.'
    exit ()

# Prime the dictionary
counts = dict()

# Compute dictionary to map each word to the count of words
for line in fhand :
    if not line.startswith('From ') : continue
    words = line.split()
    words = words[1]
    counts[words] = counts.get(words, 0) + 1

# Construct a list of (val, key) tuples
lst = list()    # note: 'lst' begins with lowercase letter 'L'
for key, val in counts.items() :
    lst.append( (val, key))  # important to note that we are switching the order (key, val) to (val, key)

# Sort the tuples list in reverse order
lst.sort(reverse=True)

# Assign tuple in (val, key) order to variables and print in swapped (key, value) order
val, key = lst[0]
print key, val