python集合常见运算案例解析

本文实例讲述了python集合常见运算。分享给大家供大家参考，具体如下：

python生成不重复随机数放在列表中的效率比较

import random
import time
def RandomNumbers(number, start, end):
  '''使用列表来生成number个介于start和end之间的不重复随机数'''
  data = []
  n = 0
  while True:
    element = random.randint(start, end)
    if element not in data:
      data.append(element)
      n += 1
    if n == number - 1:
      break
  return data
def RandomNumbers1(number, start, end):
  '''使用列表来生成number个介于start和end之间的不重复随机数'''
  data = []
  while True:
    element = random.randint(start, end)
    if element not in data:
      data.append(element)
    if len(data) == number:
      break
  return data
def RandomNumbers2(number, start, end):
  '''使用集合来生成number个介于start和end之间的不重复随机数'''
  data = set()
  while True:
    data.add(random.randint(start, end))
    if len(data) == number:
      break
  return data
start = time.time()
for i in range(1000):
  RandomNumbers(1000, 1, 10000)
print('Time used:', time.time()-start)
start = time.time()
for i in range(1000):
  RandomNumbers1(1000, 1, 10000)
print('Time used1:', time.time()-start)
start = time.time()
for i in range(1000):
  RandomNumbers2(1000, 1, 10000)
print('Time used2:', time.time()-start)

得到的结果是

==================== RESTART: C:/Users/xuzm/Desktop/比较.py ====================
Time used: 24.607422828674316
Time used1: 24.069069623947144
Time used2: 4.816216945648193
>>>

可见：

append方法对空裂变追加元素的方法效率远不及add方法