[Courses] [python] Lesson 5: Infinite loops, modulo, and random numbers
leslie.brothers at verizon.net
Sun Jul 17 16:47:37 UTC 2011
Lots of fun!!
> ====================== Homework =============================
> 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?
I couldn't quite get how to use the hint, because it seems the modulo
result depends on BOTH x and y. I will see how others used this hint.
In the meantime, I fixed it by setting a condition on the modulo result:
colors = [ 'red', 'orange', 'yellow', 'green', 'blue' ]
patch = 0
for i in range(1,5):
x = 20
while (20 % x) < 5:
patch += 1
print colors[(20 % x)],"\t","- patch no. ",patch
x -= 1
> 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.
> 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.
I made 2 classes of nouns (animate and inanimate) and 2 corresponding
classes of verbs, since they match better that way. See below.
> 4. (Optional) Change your program to add another sentence type or
> two --
I threw in some adjectives. I didn't pull out the full transformational
grammar recipes! Oops, on re-reading the question, I see I forgot to try
I'll go ahead and submit what I have, then fool around with modulo on my
> 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.
choice = raw_input("\nType 'go' if you want to see a random
sentence.\nOr, enter a name if you want a random sentence using that
name.\nType 'q' to quit.\n")
if choice == "q":
verbsan = [ 'cogitated', 'flipped out', 'vegetated', 'procrastinated',
'ruminated', 'zoned out' ]
verbsinan = [ 'mouldered', 'exploded', 'gyrated', 'vibrated' ]
nounsan = [ 'Fred', 'Pablo Escobar', 'My aunt', 'Dixie' ]
nounsinan = ['The moon', 'A water balloon', 'The traffic lights on
adjs = [ 'deadly', 'pointless', 'incomprehensible', 'tragic',
verbs = [ verbsan, verbsinan ]
nouns = [ nounsan, nounsinan ]
if choice == 'go':
if random.choice(nouns) == nouns:
print "\n",random.choice(nounsan), random.choice(verbsan)+".","It
print "\n",random.choice(nounsinan), random.choice(verbsinan)+".",
"It was", random.choice(adjs)+"."
print "\n",choice, random.choice(verbsan)+".","It
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