Python中最快的字典排序方法

代码

def sbv0(adict,reverse=False):
"""proposed at Digital Sanitation Engineering
    http://blog.modp.com/2007/11/sorting-python-dict-by-value.html"""
return sorted(adict.iteritems(), key=lambda (k,v): (v,k), reverse=reverse)

def sbv1(d,reverse=False):
"""explicit list expansion"""
    L = [(k,v) for (k,v) in d.iteritems()]
return sorted(L, key=lambda x: x[1] , reverse=reverse)

def sbv2(d,reverse=False):
"""generator"""
    L = ((k,v) for (k,v) in d.iteritems())
return sorted(L, key=lambda x: x[1] , reverse=reverse)

def sbv3(d,reverse=False):
"""using a lambda to get the key, rather than “double-assignment"""
return sorted(d.iteritems(), key=lambda x: x[1] , reverse=reverse)

def sbv4(d,reverse=False):
"""using a formal function to get the sorting key, rather than a lambda"""
def sk(x):return x[1]
return sorted(d.iteritems(), key=sk , reverse=reverse)

def sk(x): return x[1]

def sbv5(d,reverse=False):
"""using a formal function, defined in outer scope
    to get the sorting key, rather than a lambda     """
return sorted(d.iteritems(), key=sk , reverse=reverse)

from operator import itemgetter
def sbv6(d,reverse=False):
"""proposed in PEP 265, using  the itemgetter"""
return sorted(d.iteritems(), key=itemgetter(1), reverse=True)

D = dict(zip(range(100),range(100)))

from profile import run

run(“for ii in xrange(10000):  sbv0(D, reverse=True)”) 
run(“for ii in xrange(10000):  sbv1(D, reverse=True)”) 
run(“for ii in xrange(10000):  sbv2(D, reverse=True)”) 
run(“for ii in xrange(10000):  sbv3(D, reverse=True)”) 
run(“for ii in xrange(10000):  sbv4(D, reverse=True)”) 
run(“for ii in xrange(10000):  sbv5(D, reverse=True)”) 
run(“for ii in xrange(10000):  sbv6(D, reverse=True)”) 

具体的结果, 直接拷贝代码到你的本机下运行即可知道. 在我这里, sbv6的时间是0.578s, 最慢的是用generator的sbv2, 22s左右, 其他时间是差不多的, 都是11s左右.

总的来说, PEP 265 介绍的方法基本是别的方法十倍左右的速度.

 

转自：http://www.python8.org/a/fenleiwenzhang/yuyanjichu/2009/0913/318.html