On 02/17/2014 08:23 PM, "André Walker-Loud <walksl...@gmail.com>" wrote:
Hello python tutors,
I am utilizing a 3rd party numerical minimization routine. This routine
requires an input function, which takes as arguments, only the variables with
which to solve for. But I don’t want to define all possible input functions,
in a giant switch, but rather, if I know I am fitting a polynomial, I would
like to just pass a list of parameters and have the code know how to construct
this function.
To construct for example, a chisq function, you must pass not only the
variables to solve for, but also the data, uncertainties, and perhaps other
arguments. So it requires a little hacking to get it to work. With the help
of my friends and looking at similar code, I have come up with two ways that
work under my simple test cases, and I have a few questions about them.
The 3rd party minimizer utilizes the .func_code.co_varnames and
.func_code.co_argcount to determine the name and number of variables to
minimize. eg.
g = lambda x,c_0,c_1: c_0 + c_1 * x
g.func_code.co_varnames
('x', 'c_0', 'c_1’)
g.func_code.co_argcount
3
so what is needed is a function
def f(c_0,c_1):
…#construct chi_sq(c_0,c_1,x,y,…)
What prevents you to make a simple function factory (see example below) is that
the 3rd party module needs to use func_code.co_varnames & func_code.co_argcount,
right? If yes, it is indeed annoying... and I have no good solution.
# func factory example:
def poly (*coefs):
# coefs are here in reverse order for simplicity
# but we could iterate backward below
n = len(coefs)
def f (x):
y = 0
for i in range(n):
y += coefs[i] * x**i
return y
return f
# y = 3 + 2*x + 1*x^2
poly3 = poly(3,2,1)
print(poly3(1)) # 6
print(poly3(2)) # 11
print(poly3(3)) # 18
d
_______________________________________________
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor
