map函数如何与多参数处理函数配合？

代码：
import itertools
import functools
import time

def f(x,y): return x + y
RANGE_I = 800
RANGE_F = 1000
r_i = range(RANGE_I)
r_f = range(RANGE_F)

startTime = time.time()
for i in r_i:
    def f2(x): return f(x, i)
    map(f2, r_f)
endTime = time.time()
print "Finished in %f seconds!" % (endTime - startTime)

def f1(x, l): return map(lambda n: x+n, l)
startTime = time.time()
list(itertools.imap(f1, r_i, itertools.repeat(r_f)))
endTime = time.time()
print "Finished in %f seconds!" % (endTime - startTime)

startTime = time.time()
for i in r_i:
    f3 = functools.partial(f, y = i)
    map(f3, r_f)
endTime = time.time()
print "Finished in %f seconds!" % (endTime - startTime)

结果：
Finished in 0.375000 seconds!
Finished in 0.266000 seconds!
Finished in 0.593000 seconds!

似乎imap方法由于不用生成临时函数而速度快一些。

Albert Lee 写道:

> partial ?

> On 26/02/2008, jerryji wrote:
>>  As I said, itertools is a python built-in module (since 2.3).

>>  And you really should have tried it out yourself --

>>  C:\tmp>type test.py

>> from itertools import imap, repeat

>> from pprint import pprint

>>  def f(x, l):
>>     return map(lambda n: x+n, l)

>> l = list(range(10))
>>  li = list(range(3))

>>  pprint(list(imap(f, li, repeat(l))))

>>  C:\tmp>python -V
>>  Python 2.5.1

>>  C:\tmp>python test.py

>> [[0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
>>   [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
>>   [2, 3, 4, 5, 6, 7, 8, 9, 10, 11]]

>> Jerry

>>  On Feb 25, 1:02 pm, Elias Soong wrote:
>>  > 这样看起来似乎是ipython特有的功能呢。如果是CPython的话是否有其他办法呢？

>>  > jerryji 写道:

>>  > > use itertools (built-in) module --

>>  > > $ ipython

>>  > > In [1]: from itertools import imap, repeat

>>  > > In [2]: l = list(range(10))

>>  > > In [3]: l
>>  > > Out[3]: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

>>  > > In [4]: li = list(range(3))

>>  > > In [5]: li
>>  > > Out[5]: [0, 1, 2]

>>  > > In [6]: def f(x, l):
>>  > >    ....:        return map(lambda n: x+n, l)
>>  > >    ....:

>>  > > In [7]: list(imap(f, li, repeat(l)))
>>  > > Out[7]:
>>  > > [[0, 1, 2, 3, 4, 5, 6, 7, 8, 9],
>>  > >  [1, 2, 3, 4, 5, 6, 7, 8, 9, 10],
>>  > >  [2, 3, 4, 5, 6, 7, 8, 9, 10, 11]]

>>  > > Cheers,
>>  > > Jerry

>>  > > On Feb 25, 11:02 am, Elias Soong wrote:
>>  > >> 我们知道map函数可以这样用：
>>  > >> def f(x): return x+1
>>  > >> map(f,range(10))
>>  > >> 我们可以得到：[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

>>  > >> 那么如果我们定义的函数是多参数的咋办？比如：
>>  > >> def f(x,y): return x+y
>>  > >> 然后希望在map里面调用f的时候可以指定其中一个参数的值。。作用在数组上。。

>>  > >> 想到的一个办法是利用原多参数函数定义在调用map函数之前指定部分参数来做一
>>  > >> 个临时函数。。比如变成这样：
>>  > >> def f(x,y): return x+y
>>  > >> for i in range(3):
>>  > >>      def f2(x): return f(x,i)
>>  > >>      map(f2,range(10))
>>  > >> 于是得到：
>>  > >> [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>  > >> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
>>  > >> [2, 3, 4, 5, 6, 7, 8, 9, 10, 11]

>>  > >> 有没有其他办法使map函数与多参函数配合呢？

>>  > >> ----------------------------------------
>>  > >> ----------------------------------------

>>  > ----------------------------------------
>>  > ----------------------------------------