python - 我什么时候应该更喜欢 random.choice() 而不是 random.randint？

Question

考虑从消息列表中打印随机字符串的以下两个选项:

import random

messages = ['It is certain',
    'It is decidedly so',
    'Yes definitely',
    'Reply hazy try again',
    'Ask again later',
    'Concentrate and ask again',
    'My reply is no',
    'Outlook not so good',
    'Very doubtful']


print(messages[random.randint(0, len(messages) - 1)])  # option 1

print(random.choice(messages))                         # option 2

选项 1 和选项 2 产生相同的效果。有理由偏爱其中一个吗？性能怎么样？一个比另一个更有效吗？

Answer 1

一些时间分析:

from timeit import timeit

setup = """
import random
import string
s = string.ascii_lowercase
x = [s[:random.randint(1, 26)] for _ in range(10_000)]
"""
stmt1 = """
random.choice(x)
"""

stmt2 = """
x[random.randint(0, len(x) - 1)]
"""

for i in range(0, 100_000, 10_000):
    print(f"Size_seq: {i}")
    print(f"    choice: {timeit(stmt = stmt1, setup = setup, number = i):>.5}s")
    print(f"    randint: {timeit(stmt = stmt2, setup = setup, number = i):>.5}s")

输出:

Size_seq: 0
    choice: 1.426e-06s
    randint: 1.672e-06s
Size_seq: 10000
    choice: 0.010363s
    randint: 0.017393s
Size_seq: 20000
    choice: 0.020168s
    randint: 0.034601s
Size_seq: 30000
    choice: 0.030942s
    randint: 0.050896s
Size_seq: 40000
    choice: 0.041753s
    randint: 0.069362s
Size_seq: 50000
    choice: 0.053554s
    randint: 0.088815s
Size_seq: 60000
    choice: 0.067187s
    randint: 0.10979s
Size_seq: 70000
    choice: 0.080606s
    randint: 0.12793s
Size_seq: 80000
    choice: 0.083252s
    randint: 0.1365s
Size_seq: 90000
    choice: 0.091724s
    randint: 0.14603s

这种差异在大范围内是显着的。因此，如果输入不是很大，您可以使用它们中的任何一个，但是当大小增加时，randint 比 random.choice 慢得多。