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

[Kay Nettle]

 >
 >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?

colors = [ "red", "orange", "yellow", "green", "blue" ]
lenght=len(colors)
for i in range(20):
	print colors[i % lenght]


 >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.

import os, random
dir="/usr/share/backgrounds"

if os.path.isdir(dir):
	print random.choice(os.listdir(dir))


 >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".
 
I don't have the grammer gene, so I stopped reading the instructions.  I
wrote something that did have some nouns and verbs, but I read from a
file or files...sorry (and I played with argparse).

 #!/usr/bin/python

import argparse, random, os, string

nouns=[]
verbs=[]

nouns_default=['the cat', 'the dog', 'the dog who eats pillows', 'the man', 'the girl']
verbs_default=['ate a pillow', 'ran', 'barked']

def read_file(file_name, word_list):
	if not os.path.isfile(file_name):
		print "%s is not a filename" % (file_name)
		sys.exti(1)
	else:
		file = open(file_name, "r")
		for line in file:
			line=line.lstrip()
			line=line.rstrip(' ' '\n')
			if not line:
				continue
			word_list.append(line)

		file.close()

	return word_list	

parser = argparse.ArgumentParser(description='Print sentences with \
random verbs and nouns (will use built in list if no files are given)')
parser.add_argument('-n','--nouns', dest='noun_file', action='store', \
 type=str, default="", help='file with nouns on on a line')
parser.add_argument('-v','--verb', dest='verb_file', action='store', \
 type=str, default="", help='file with verbs with verbs one on a line')
parser.add_argument('-t','--times', dest='count', action='store', type=int, \
 default=1, help='number of sentences you want generated')
args = parser.parse_args()
 
if args.noun_file:
	read_file(args.noun_file,nouns)	
else:
	nouns=nouns_default

if args.verb_file:
	read_file(args.verb_file,verbs)
else:
	verbs=verbs_default

for i in range(args.count):
	print random.choice(nouns), random.choice(verbs)