Arrays--part 3.

To create an array:
words = ["horse", "dog", "cow"]
creates a list with 3 elements--you can reference these elements singly as words[0], words[1],
and words[2].
so, for example:
for i in range(3):
       print words[i]
would print out the words in this list.  If you want to add a 4th word, "heffalump", you can do
words.append("heffalump")
and heffalump becomes words[3], so there are now 4 words in the list. 
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A more flexible way of having a list in your program is to create on in your Python IDLE GUI:
horse
dog
pig
heffalump
woozle
etc   one word per line--call this, say, mywords.txt (it's NOT a Python program, but a data set).
Then to read in the words:

words = []                                                   this creates an initial empty list
numwds = 0                                                we'll keep track of how many words there are
file = open('mywords.txt')                      this opens the data file for reading
for line in file:                                            a variation on a for loop
      words.append(line)                             adds the word to the list
      numwds = numwds + 1                      keeps track of how many words we have so far

We can then do
for j in range(numwds):
        print words[j]                                   to print out all the words
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If you want to write the words to another file:

outfile = open('copy.txt','w')                opens the file for writing
for j in range(numwds):
       outfile.write(words[j])
outfile.close()                                              closes the file

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what also works for input is

file = open('mywords.txt','r')
for line in file.readlines():
        words.append(line)
        numwds = numwds + 1

there are also other variations