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.

@Alexander, I've update my question, could you see it again? — ZK Zhao
– ZK Zhao, Commented Sep 14, 2015 at 2:50

Serdalis · Accepted Answer · 2015-09-14 02:54:41Z

2

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 )

edited Sep 14, 2015 at 2:54

answered Sep 14, 2015 at 2:44

Serdalis

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2 Comments

ZK Zhao Over a year ago

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 Over a year ago

Ah in that case, you don't need to do anything special, I've edited my answer.

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