Python: Separate list into variables

Question

How can I turn

def square_error(f1,f2, u1,v1,sigu1,sigv1,rho1, u2,v2,sigu2,sigv2,rho2, u3,v3,sigu3,sigv3,rho3):

into:

def square_error(x):
# x = [0.2,0.5,
# 1,1,1,1,0.3,
# 1,1,1,1,0.3,
# 1,1,1,1,0.3],
 f1,f2, u1,v1,sigu1,sigv1,rho1, u2,v2,sigu2,sigv2,rho2, u3,v3,sigu3,sigv3,rho3 = x

The scipy.minimize function only allow 1 argument for the target function, so I need to turn the variables into a single argument.

• Barmar: possible duplicate of *args and **kwargs?
• Alexander: np.array(x)? I'm not clear what you're asking.
• ZK Zhao: @Alexander, I've update my question, could you see it again?

Answer 1

Yes you can do that, but you will have to the * syntax which will unpack the array into the parameters of the function.

For example:

def square_error( x,y,z ):
 print x,y,z
arr = [ 1, 2, 3 ]
square_error( *arr )

will unpack the values 1,2,3 into the parameters x,y,z

---

Or if you wanted to unpck the values into variables within the function, use sequence unpacking:

def square_error( arr ):
 x,y,z = arr
 print x,y,z
arr = [ 1, 2, 3 ]
square_error( arr )

• ZK Zhao: I'm sorry, I may not be cleaer enough. I need to turn def square_error(x,y,z): into def square_error(x):, and within the function, unpack the x into x,y,z. How can I do that? The scipy.minimize function seems only allow for 1 argument.
• Serdalis: Ah in that case, you don't need to do anything special, I've edited my answer.