How can I get rid of lambda

[Robert Roy]

I went a step further with your code and created a lookup dict for all
256 char values. 100,000 reps went from 9.2 seconds to 3.9 seconds.

Append the following to the code you posted
#--------------
# create a dict of characters and expansions 
l = {}
for x in range(256):
    l[chr(x)] = unpack(chr(x))
#print l    
#print map(None, packedNumber)    

# do some timing
import time
# so the range call does not influence the timing
reps = range(100000)

# test using unpack
s = time.clock()
for x in reps:
    unpack(packedNumber)
t = time.clock()
print 'using unpack', t-s

#test using the dict, note there is no need for function call
# get rid of the dot
lget = l.get
s = time.clock()
for x in reps:
    fnJoin(map(lget, packedNumber), '')
t = time.clock()
print 'using dict.get', t-s






On Mon, 16 Oct 2000 00:11:29 GMT, Steve Williams
<sandj.williams at gte.net> wrote:

>I'm working with IBM packed decimal data.  The following code works OK,
>but there are millions of rows and 10 to 50 columns per row.  I want as
>much speed as I can get.
>
>How can I avoid the lambda in the following unpack function?  Or better,
>is there a faster way?
>
>By the way, if you want a testimonial to Python's capabilities, do a
>Google search on 'packed decimal' and have a look at some of the Java
>solutions to this problem.
>
>===============================================
>
>"""Unpack an IBM packed decimal string"""
>import string
>
>#Get rid of the dots
>fnJoin = string.join
>fnTranslate = string.translate
>
>#Create translate tables for the left and right nybbles
>_strSource = ""
>for _i in range(256): _strSource = _strSource + chr(_i)
>_trtLeftNybble = string.maketrans(_strSource, \
>    "0"*16  + "1"*16 + "2"*16 + "3"*16 + "4"*16 + \
>    "5"*16 + "6"*16 + "7"*16 + "8"*16 + "9"*16 + "."*96)
>_trtRightNybble = string.maketrans(_strSource,"0123456789+-+-++"*16)
>del _strSource
>del _i
>
>def unpack(strPacked):
>    return fnJoin(map(lambda chrLeft, chrRight: chrLeft + chrRight,\
>        fnTranslate(strPacked,_trtLeftNybble),\
>        fnTranslate(strPacked,_trtRightNybble)),"")
>
>try:
>    packedNumber = '\x01\x23\x45\x67\x89\x0f'
>    print unpack(packedNumber)
>except RuntimeError, e:
>    print e
>
>try:
>    packedNumber = '\x01\x23\x45\x67\x89\x0d'
>    print unpack(packedNumber)
>except RuntimeError, e:
>    print e
>
>
>