排序常用方法

• 列表内置函数sort

# sort是会影响列表本身
lis = [4,5,68,46,4,]
lis.sort()
print(lis)
[4, 4, 5, 46, 68]

sorted

• 字典排序

dic = {0: 9, 1: 0, 2: 3, 3: 3, 4: 1, 5: 7, 6: 4}
# 将字典items键值对组成元组传入，取每个元组[1]元素进行排序，reverse表示升降序
b = dict(sorted(dic.items(),key=lambda x:x[1],reverse=True))
print(b)
{0: 9, 5: 7, 6: 4, 2: 3, 3: 3, 4: 1, 1: 0}

• 列表内嵌字典

portfolio = [
    {'name': 'IBM', 'shares': 100, 'price': 91.1},
    {'name': 'AAPL', 'shares': 50, 'price': 543.22},
    {'name': 'FB', 'shares': 200, 'price': 21.09},
    {'name': 'HPQ', 'shares': 35, 'price': 31.75},
    {'name': 'YHOO', 'shares': 45, 'price': 16.35},
    {'name': 'ACME', 'shares': 75, 'price': 115.65}
]

a = sorted([i for i in portfolio],key=lambda x:x['price'],reverse=True)

print(a)

• 模块heapq方法
  • 传入三个参数， nsmallest(n, iterable, key=None)
  • n -> 排序的数量
  • iterable -> 要排序的可迭代对象
  • key -> 排序的关键字

import heapq

portfolio = [
    {'name': 'IBM', 'shares': 100, 'price': 91.1},
    {'name': 'AAPL', 'shares': 50, 'price': 543.22},
    {'name': 'FB', 'shares': 200, 'price': 21.09},
    {'name': 'HPQ', 'shares': 35, 'price': 31.75},
    {'name': 'YHOO', 'shares': 45, 'price': 16.35},
    {'name': 'ACME', 'shares': 75, 'price': 115.65}
]
# 升序

cheap = heapq.nsmallest(len(portfolio),portfolio, key=lambda s: s['price'])
print(cheap)
[{'name': 'YHOO', 'price': 16.35, 'shares': 45},
 {'name': 'FB', 'price': 21.09, 'shares': 200},
 {'name': 'HPQ', 'price': 31.75, 'shares': 35},
 {'name': 'IBM', 'price': 91.1, 'shares': 100},
 {'name': 'ACME', 'price': 115.65, 'shares': 75},
 {'name': 'AAPL', 'price': 543.22, 'shares': 50}]

# 降序
expensive = heapq.nlargest(3, portfolio, key=lambda s: s['price'])
print(expensive)
[{'name': 'AAPL', 'price': 543.22, 'shares': 50},
 {'name': 'ACME', 'price': 115.65, 'shares': 75},
 {'name': 'IBM', 'price': 91.1, 'shares': 100}]