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Sage: christoffel symbol calculation issue, help...

asked 2016-03-03 15:19:04 -0500

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I got this trying to compute the example christoffel symbols sage:

sage: var('r t theta phi')
(r, t, theta, phi)
sage: (r, t, theta, phi)
(r, t, theta, phi)
sage: sage: m = matrix(SR, [[(1-1/r),0,0,0],[0,-(1-1/r)^(-1),0,0],[0,0,-r^2,0],[0,0,0,-r^2*(sin(theta))^2]])
sage: sage: print m
[ -1/r + 1 0 0 0]
[ 0 1/(1/r - 1) 0 0]
[ 0 0 -r^2 0]
[ 0 0 0 -r^2*sin(theta)^2]
sage: [ -1/r + 1 0 0 0]

Moreover, I get...

sage: var('r t theta phi')
(r, t, theta, phi)
sage: m = matrix(SR, [[(1-1/r),0,0,0],[0,-(1-1/r)^(-1),0,0],[0,0,-r^2,0],[0,0,0,-r^2*(sin(theta))^2]])    
sage: def christoffel(i,j,k,vars,g):
....:        s = 0
....:        ginv = g^(-1)
....:        for l in range(g.nrows()):
....:               s = s + (1/2)*ginv[k,l]*(g[j,l].diff(vars[i])+g[i,l].diff(vars[j])-g[i,j].diff(vars[l]))
....:            return s
....:     
  File "<ipython-input-3-70e0eaa76f50>", line 6
    return s
            ^
IndentationError: unindent does not match any outer indentation level

What am I doing BAD?

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Comments

1

In Python, which is the underlying base language of sage code block is determined by indentation. In your case the return statement should be at the same level (same column) as the for statement.

DBS gravatar imageDBS ( 2016-03-03 21:58:09 -0500 )edit

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answered 2016-03-03 15:29:13 -0500

tmonteil gravatar image

updated 2016-03-03 15:30:14 -0500

The error says it all (IndentationError) : in Python, the indentation is very important. In your case, the return s should start at the same text column than for l in range(g.nrows()):

In general, it is advised to indent with 4 spaces, so, your code should look like:

sage: def christoffel(i,j,k,vars,g):
....:     s = 0
....:     ginv = g^(-1)
....:     for l in range(g.nrows()):
....:         s = s + (1/2)*ginv[k,l]*(g[j,l].diff(vars[i])+g[i,l].diff(vars[j])-g[i,j].diff(vars[l]))
....:     return s
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Asked: 2016-03-03 15:19:04 -0500

Seen: 129 times

Last updated: Mar 03 '16