A201/A597 Introduction to Programming I (4/3 cr.)

Second Summer 2006

Lecture Notes Nine: Dictionaries, methods, files.

Today we will discuss, in order:

dictionaries
methods (functions)
text files

So here are some programs we will develop:

message = raw_input("Give me the word: ")
dictionary = {}
for e in message:
    if dictionary.has_key(e):
        dictionary[e] = dictionary[e] + 1
    else :
        dictionary[e] = 1
print "I have built the dictionary:"
for e in dictionary.keys():
    print "Letter " + e + " occurs " + str(dictionary[e])
letter = raw_input("Give me the letter: ")
if dictionary.has_key(letter):
    print "Letter " + letter + " occurs " + str(dictionary[letter]) + " times in " + message
else:
    print "Letter " + letter + " does not occur in " + message

print "Again:"

count = 0
for e in message:
    if letter == e:
        count = count + 1
print count

Here's how this program works:

Give me the word: stupendous
I have built the dictionary:
Letter p occurs 1
Letter s occurs 2
Letter u occurs 2
Letter t occurs 1
Letter d occurs 1
Letter e occurs 1
Letter o occurs 1
Letter n occurs 1
Give me the letter: u
Letter u occurs 2 times in stupendous
Again:
2

>>>

The next program finds the longest line in a file:

in terms of number of characters
in terms of number of non-space characters
in terms of number of tokens in a line

Here's how it looks:

def tokens(line):
    tokens = line.split()
    return len(tokens)

def nonspace(line):
    tokens = line.split()
    sum = 0
    for token in tokens:
        sum = sum + len(token)
    return sum

file = open("C:/Documents and Settings/dgerman/Desktop/rem.txt", "r")
bob = ""
jim = ""
tom = ""
for line in file:
    if len(line) > len(bob):
        bob = line
    if tokens(line) > tokens(jim):
        jim = line
    if nonspace(line) > nonspace(tom):
        tom = line
file.close()

print bob
print jim
print tom

And if the file looks like this:

I've watched the stars fall silent from your eyes
All the sights that I have seen
I can't believe that I believed I wished
T h a t  y o u  c o u l d  s e e 
There's a new planet in the solar system
There is nothing up my sleeve

                      I'm pushing an elephant up the stairs
I'm tossing up punch lines that were never there
Over my shoulder a piano falls
Crashing to the ground

then the lines printed will be no. 1, 4 and 8 (not in that order).

Last updated: June 28, 2006 by Adrian German for A201/A597