"Gordon Williams" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED] > Hi, > > I have to lists that I need to find the common numbers (2nd rounded to > nearest integral) and I am wondering if there is a more efficient way of > doing it. > > >>> a= [(123,1.3),(123,2.4),(123,7.8),(123,10.2)] > >>> b= [(123, 0.9), (123, 1.9), (123, 8.0)] > >>> [ (i,round(j)) for i,j in a for l,m in b if (i,round(j)) == > (l,round(m))] > [(123, 1.0), (123, 2.0), (123, 8.0)] > >>> > This works but a and b can be in the order of 30K long. > > A couple of other bits of info. > - a and b are ordered smallest to largest (could bisect module be used?) > - in the future I will want to round the second number of closest 0.25 > rather than whole number. > > Would the sets module be more efficient?
Yes: >>> set((x,round(y)) for x,y in a) & set((x,round(y)) for x,y in b) set([(123, 8.0), (123, 2.0), (123, 1.0)]) > I'm using python 2.3. >>> from sets import Set as set >>> set([(x,round(y)) for x,y in a]) & set([(x,round(y)) for x,y in b]) set([(123, 8.0), (123, 2.0), (123, 1.0)]) Raymond Hettinger -- http://mail.python.org/mailman/listinfo/python-list
