'''
Exercise 9.1 Write a function that reads the words in words.txt and stores them as keys in a
dictionary. It doesn’t matter what the values are. Then you can use the in operator as a fast way to check whether a string is in the dictionary.
'''
f1=open('words.txt')
d1=dict()
i=0
for line in f1:
    words=line.split()
    for i in range(len(words)):
        d1[words[i]]=i
print d1
print 'abc' in d1

'''
Exercise 9.2 Dictionaries have a method called get that takes a key and a default value. If
the key appears in the dictionary, get returns the corresponding value; otherwise it returns the
default value.
Use get to write histogram more concisely. You should be able to eliminate the if statement.
'''
def histogram(s):
    d = dict()
    for c in s:
        d[c]=d.get(c,0)+1
    return d
print histogram('abbcccdddd')

'''
Exercise 9.3 Write a program that categorizes each mail message by which day of the week
the commit was done. To do this look for lines which start with “From”, then look for the third
word and then keep a running count of each of the days of the week. At the end of the program
print out the contents of your dictionary (order does not matter).
'''
f1=open('mail.txt')
d1=dict()
for line in f1:
    words=line.split()
    if words[0]=='From':
        d1[words[2]]=d1.get(words[2],0)+1
    else:
        continue
print d1

'''
9.4 Write a program to read through a mail log, and figure out who had the most
messages in the file. The program looks for “From” lines and takes the second parameter on
those lines as the person who sent the mail.
The program creates a Python dictionary that maps the sender’s address to the total number of
messages for that person.
After all the data has been read the program looks through the dictionary using a maximum loop
(see Section 5.7.2) to find who has the most messages and how many messages the person has.
'''
f1=open('mail.txt')
d1=dict()
for line in f1:
    words=line.split()
    if words[0]=='From':
        d1[words[1]]=d1.get(words[1],0)+1
    else:
        continue
print d1

'''
Exercise 9.5 This program records the domain name (instead of the address) where the message
was sent from instead of who the mail came from (i.e. the whole e-mail address). At the end of
the program print out the contents of your dictionary.
'''
f1=open('mail.txt')
d1=dict()
for line in f1:
    words=line.split()
    if words[0]=='From':
        a=line.find('@')
        b=line.find(' ',a);
        c=line[a+1:b]
        d1[c]=d1.get(c,0)+1
    else:
        continue
print d1