What does random.sample() method in python do?

问题:

I Googled it a lot but could not found it. I want to know the use of random.sample() method and what does it give? When should it be used and some example usage.

回答1:

According to documentation:

random.sample(population, k)

Return a k length list of unique elements chosen from the population sequence. Used for random sampling without replacement.

Basically, it picks k unique random elements, a sample, from a sequence:

>>> import random
>>> c = list(range(0, 15))
>>> c
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]
>>> random.sample(c, 5)
[9, 2, 3, 14, 11]

random.sample works also directly from a range:

>>> c = range(0, 15)
>>> c
range(0, 15)
>>> random.sample(c, 5)
[12, 3, 6, 14, 10]

In addition to sequences, random.sample works with sets too:

>>> c = {1, 2, 4}
>>> random.sample(c, 2)
[4, 1]

However, random.sample doesn't work with arbitrary iterators:

>>> c = [1, 3]
>>> random.sample(iter(c), 5)
TypeError: Population must be a sequence or set.  For dicts, use list(d).

回答2:

random.sample() also works on text

example:

> text = open("textfile.txt").read() 

> random.sample(text, 5)

> ['f', 's', 'y', 'v', '\n']

\n is also seen as a character so that can also be returned

you could use random.sample() to return random words from a text file if you first use the split method

example:

> words = text.split()

> random.sample(words, 5)

> ['the', 'and', 'a', 'her', 'of']