Hello, I have been using scipy for about one and a half years now and have been extremely pleased. In this time I have made extensive use of scipy.optimize.leastsq. While I am generally fairly happy with its performance, I think it does lacks one important feature which I am used to from similar routines in other languages. (Please excuse if I have just missed that feature so far.) I would like to be able to control which parameters actually are fitted. For example I would like to be able to do leastsq( redsiduals, p0, args=(y), fit=([True,True,False,True]) ) where the parameter "fit" would tell leastsq to leave the parameter p0[2] untouched while fitting the others. Right now I have to modify my source code to change the parameters which are actually fit. I'd be happy to participate and start getting my hands dirty if someone would point out where to start. Regards, Maximilian