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python random recursion

Python recursive function doesn't return random choice

发布于 2020-04-10 10:20:47

I am trying to get random work in python using random module. My function is as below:

import random

word_file = "/usr/share/dict/words"
WORDS = open(word_file).read().splitlines()


def get_random_word(max_length=None):
    word = random.choice(WORDS)
    print(word)

    if not max_length:
        return word

    if len(word) > max_length:
        get_random_word(max_length)

    return word

When I import this function in ipython console and run as get_random_word(max_length=5), I get this result:

Latasha's
Hammond's
evacuated
aviary
misconducted
airfare's
controllable
unduly
gaunt
Out[32]: "Latasha's"

As you see from output, function calls itself until it finds the word with length less than 5. But at the end it returns very first random word. What is wrong with my function?

Questioner
nicat9507
Viewed
46
分享
chepner 2020-02-01 23:23

Recursion in Python is inefficient, due to repeated calls to user-defined functions, and limited, in that you will eventually overflow the stack if you don't terminate the recursion soon enough. As such, while the fix to your problem is trivial (return the return value of the recursive call), it's a moot point because recursion is the wrong approach to begin with.

Instead, use a while loop to call random.choice until you get a word that fits your condition.

import random

word_file = "/usr/share/dict/words"
WORDS = open(word_file).read().splitlines()


def get_random_word(max_length=None):
    while True:
        word = random.choice(WORDS)
        if max_length is None or len(word) <= max_length:
            return word
nicat9507 2020-02-01 23:45:21

Thanks for your help.

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