how can i randomly print an element from a list in python

Question

So far i have this, which prints out every word in my list, but i am trying to print only one word at random. Any suggestions?

def main():
    # open a file
    wordsf = open('words.txt', 'r')
    word=random.choice('wordsf')
    words_count=0
    for line in wordsf:
        word= line.rstrip('\n')
        print(word)
        words_count+=1      

    # close the file
    wordsf.close()

Answer 1

Try:

print random.choice([x.rstrip() for x in open("words.txt")])

Note that this strips the '\\n' from every line before choosing a random one; a better solution is left as an exercise for the reader.

Answer 2

To print one random word per line, your loop could be:

for line in wordsf:
    word = random.choice(line.split())
    print(word)

If there are lines with nothing but whitespace, you also need to skip those:

for line in wordsf:
    if line.isspace(): continue
    word = random.choice(line.split())
    print(word)

The counting part you have seems to be correct, but unrelated to your question.

Edit : I see you meant something different in your Q (as other A's also intepreted): you want to choose a random line from the file, not a random word from each lines. That being the case, the other A's are correct, but they take O(N) auxiliary memory for a file of N lines. There's a nice algorithm due to Knuth to pick a random sample from a stream without knowing in advance how many items it has (unfortunately it requires generating N random numbers, so it's slower than the simpler one if you have enough memory for the latter... but it's still interesting to consider!-)...:

n = 0
word = None
for line in wordsf:
    n += 1
    if random.randrange(n) == 0:
        word = line
print(word.strip())

Basically, at each line n , we're picking it to replace the previous one (if any) with a probability of 1.0/n -- so the first time probability 1 (certainty), the second time probability 0.5, and so on. I'm doing the stripping only at the end as it would be a waste of effort to strip temporary choices that are later replaced; and I'm avoiding the division and floating point hassles by generating a random number with uniform probability between 0 and n-1 included (so the probability of that random number being 0 is 1/n ) -- minor issues, but since they don't make the code any less clear, we might as well take care of them;-).

Answer 3

import random
def main():
    wordsf = open('words.txt', 'r')
    words = [line.rstrip('\n') for line in wordsf]
    wordsf.close()

    random_number = random.randint(0, len(words)-1)
    random_word = words[random_number]
    print random_word

This works well, but if the file wordsf is too huge, then I think you'll start to encounter memory issues, but I think this should do fine for most cases

Hope this helps.