python sorted排序

讲一下python里的sorted排序

a = [
    {"time": "2012-12-12 00:00:00"},
    {"time": "2012-12-14 00:00:00"},
    {"time": "2012-12-16 00:00:00"},
    {"time": "2012-12-18 00:00:00"},
    {"time": "2012-12-16 00:00:00"},
    {"time": "2012-12-17 00:00:00"},
    {"time": "2012-12-10 00:00:00"},
    {"time": "2012-12-11 00:00:00"},
]

b = sorted(a, key=lambda d: d['time'])

b = [
    {'time': '2012-12-10 00:00:00'},
    {'time': '2012-12-11 00:00:00'},
    {'time': '2012-12-12 00:00:00'},
    {'time': '2012-12-14 00:00:00'},
    {'time': '2012-12-16 00:00:00'},
    {'time': '2012-12-16 00:00:00'},
    {'time': '2012-12-17 00:00:00'},
    {'time': '2012-12-18 00:00:00'}
]

sorted里key接受的是一个函数，排序的时候，将key接收的函数分别作用于序列的子内容，然后通过key函数返回值排序。
如上所示，实际上sorted函数排序的是每个{"time":"xxxx"}的time值
亦可通过下面的快排实现

def QuickSort(L, low, high):
    """专用快排"""
    i = low
    j = high
    if i >= j:
        return L
    key = L[i]
    while i < j:
        while i < j and L[j]["time"] >= key["time"]:
            j = j - 1
        L[i] = L[j]
        while i < j and L[i]["time"] <= key["time"]:
            i = i + 1
        L[j] = L[i]
    L[i] = key
    QuickSort(L, low, i - 1)
    QuickSort(L, j + 1, high)
    return L[::-1]

def fun(a, b):
    if a["time"] > b["time"]:
        return -1
    else:
        return 1

c=sorted(a, cmp=fun)

c=[
    {'time': '2012-12-18 00:00:00'}, 
    {'time': '2012-12-17 00:00:00'}, 
    {'time': '2012-12-16 00:00:00'}, 
    {'time': '2012-12-16 00:00:00'},   
    {'time': '2012-12-14 00:00:00'}, 
    {'time': '2012-12-12 00:00:00'}, 
    {'time': '2012-12-11 00:00:00'}, 
    {'time': '2012-12-10 00:00:00'}
]

c=sorted(a, cmp=fun)意思是遍历a列表的时候，分别取相邻的两个数带入fun函数中 如果fun函数返回的是正数，则交换相邻的两个数据，反之，不交换

sorted还有个reverse参数，表示是否逆序，默认为reverse=False 升序排列。

sort方法也一样有这些功能