# Debug (sympy-Function; lambdify)

S

#### Surbhi Gupta

This is the code I m trying to run:

from sympy import *
import numpy as np
from sympy import symbols

def deriv(x,t):
a = array(x)
for i in range(0,len(x)):
temp = x
a = temp.diff(t)
return a

def matrixmult (A, B):
C = [[0 for row in range(len(A))] for col in range(len(B))]
for i in range(len(A)):
for j in range(len(B)):
for k in range(len(B)):
C[j] += A[k]*B[k][j]
return C

l1,l2,m1,m2,t = symbols('l1,l2,m1,m2,t')
g = 10

th1 = Function('th1')(t)
th2 = Function('th2')(t)
th1dot = Derivative(th1, t)
th2dot = Derivative(th2, t)

x1 = array([[l1*sin(th1)], [-l1*cos(th1)]])
x2 = x1 + array([[l2*sin(th1 + th2)], [-l2*cos(th1 + th2)]])
x1dot = deriv(x1, t)
x2dot = x1dot + deriv(x2, t)

temp1 = matrixmult(x1dot.T,x1dot)
temp2 = matrixmult(x2dot.T, x2dot)
kin = (1/2.0)*m1*temp1 + (1/2.0)*m2*temp2
pot = -m1*g*l1*cos(th1) -m2*g*(l1*cos(th1) + l2*cos(th1+th2))
L = kin - pot

e = lambdify((t, l1, l2, m1, m2, th1, th2), L)

all other commands of above code run with no error. but as soon as I give last command (the lambdify 1) I get a syntax error. I think that is because I m using th1 and th2 as Function of t. Can anyone help me on how to solve this?

M

#### Marco Buttu

This is the code I m trying to run:

from sympy import *
import numpy as np
from sympy import symbols

def deriv(x,t):
a = array(x)
for i in range(0,len(x)):
temp = x
a = temp.diff(t)
return a

def matrixmult (A, B):
C = [[0 for row in range(len(A))] for col in range(len(B))]
for i in range(len(A)):
for j in range(len(B)):
for k in range(len(B)):
C[j] += A[k]*B[k][j]
return C

l1,l2,m1,m2,t = symbols('l1,l2,m1,m2,t')
g = 10

th1 = Function('th1')(t)
th2 = Function('th2')(t)
th1dot = Derivative(th1, t)
th2dot = Derivative(th2, t)

x1 = array([[l1*sin(th1)], [-l1*cos(th1)]])
x2 = x1 + array([[l2*sin(th1 + th2)], [-l2*cos(th1 + th2)]])
x1dot = deriv(x1, t)
x2dot = x1dot + deriv(x2, t)

temp1 = matrixmult(x1dot.T,x1dot)
temp2 = matrixmult(x2dot.T, x2dot)
kin = (1/2.0)*m1*temp1 + (1/2.0)*m2*temp2
pot = -m1*g*l1*cos(th1) -m2*g*(l1*cos(th1) + l2*cos(th1+th2))
L = kin - pot

e = lambdify((t, l1, l2, m1, m2, th1, th2), L)

all other commands of above code run with no error. but as soon as I give last command (the lambdify 1)
I get a syntax error. I think that is because I m using th1 and th2 as Function of t. Can anyone help me on how to solve this?

There is just one error for me: array instead of np.array. Once changed
this, it works fine (Python 3.3, SymPy 0.7.3)