[Courses] [python] Lesson 5: Infinite loops, modulo, and random numbers

[Prana Peddi]

My answers below: I did not use modulo in question 4 below.

1. Suppose you have a list of colors, like
>   colors = [ "red", "orange", "yellow", "green", "blue" ]
>   and you have a bunch of things (say, 20 of them) that you
>   need to color without repeating. How would you use the modulo
>   operator, %, to step through the colors in order, printing out one
>   after another and going back to red after blue?
>
>   Hint: remember, x % y always gives you a number between 0 and y.
>   What does y have to be so that it always gives you something that
>   could be an index of the list?
>

colors = ["red", "orange", "yellow", "green", "blue"]
for i in range(0,20):
        j = i % len(colors)
        print "item {0} needs to have color {1}.".format(i, colors[j])

2. How would you write a program to choose a random file from a
>   directory full of files? Assume the directory is in some fixed place,
>   like "/usr/share/backgrounds" or "/home/yourname/Backgrounds".
>   Hint: os.listdir(dirname) will give you a list of all the files in
>   a directory. Of course you have to import os first.
>
>   Why would you want to do this? In my case, I have a big collection
>   of desktop background images, and every time I log in, I have a
>   script that gives me a different wallpaper image that day. (I use
>   hsetroot -center filename to set the wallpaper under openbox; Gnome
>   or KDE users might need a different method.) It's fun to see what
>   image I'll get each day.  For a while I did the same thing with my
>   beep tone, so if anything happened to make my computer beep, I
>   might hear a crow or a wolf or a grey whale. But it drove my
>   husband crazy, so I stopped in the name of marital harmony.
>
import os
import random

filelist = os.listdir(".")
print "randomly chose the file: {0}".format(random.choice(filelist))

3. Make a list of nouns and a list of verbs. Then write a program that
>   makes a random sentence by choosing a random noun and a random verb.
>
>   You may notice that my verbs are intransitive -- they can be used on
>   their own. So you can say "the cat waited", whereas a noun-verb sentence
>   wouldn't work if you used a transitive verb like "the cat fixed".
>
> import random

noun = [ "I", "The clock", "The sun", "John"]
intran_verb = [ "ran", "waited", "glowed", "shined" ]

print "{0} {1}".format(random.choice(noun), random.choice(intran_verb))


> 4. (Optional)  Change your program to add another sentence type or
>   two -- maybe add a list of transitive verbs and make it sometimes
>   choose noun-trans verb-noun sentences, other times just
>   noun-intrans verb sentences. Or add a list of adjectives and add
>   adjectives to your sentences. How would you use random and modulo
>   together to say "sometimes do this type of sentence, other times
>   do this type"?
>
>   The object here is to have fun writing a program that makes
>   interesting, wacky sentences.
>
>   If you get ambitious and want to spend some more time, try do this
>   in a loop, taking input from the user each time, and let the user
>   quit by typing q or quit or whatever.  You could even ask the user
>   for a noun or verb and then make a sentence using it.
>

import random

article =       [ "a", "the", "an"]
subject =       [ "clock", "sun", "John", "Jane", "baby"]
intran_verb =   [ "ran", "waited", "glowed", "delayed" ]
tran_verb =     [ "fixed", "played", "hit", "rang" ]
obj =           [ "me", "song", "game", "ball", "drum", "bell" ]
adjective =     ["beautiful", "stupid", "weak", "kind", "lively" ]

sentence =      [
                "{0} {1}.".format(random.choice(subject),
random.choice(intran_verb)),
                "{0} {1} {2}.".format(random.choice(subject),
random.choice(tran_verb), random.choice(obj)),
                "{0} {1} {2} {3}.".format(random.choice(subject),
random.choice(tran_verb), random.choice(adjective),
                 random.choice(obj)),
                "{0} {1} {2}.".format(random.choice(article),
random.choice(subject), random.choice(intran_verb)),
                "{0} {1} {2} {3} {4}.".format(random.choice(article),
random.choice(subject), random.choice(tran_verb),
                random.choice(article), random.choice(obj)),
                "{0} {1} {2} {3} {4} {5}.".format(random.choice(article),
random.choice(subject),
                random.choice(tran_verb), random.choice(article),
random.choice(adjective), random.choice(obj)),
                ]

while (True) :
        inp = raw_input("q to quit, enter to continue\n")
        if (inp == "q") :
                print "quiting"
                break
        else :
                print random.choice(sentence)