Q:

Is MATLAB faster than Python?

I want to compute magnetic fields of some conductors using the Biot–Savart law and I want to use a 1000x1000x1000 matrix. Before I use MATLAB, but now I want to use Python. Is Python slower than MATLAB ? How can I make Python faster? 
EDIT:
Maybe the best way is to compute the big array with C/C++ and then transfering them to Python. I want to visualise then with VPython. 
EDIT2: Which is better in my case: C or C++? 

A:

You might find some useful results at the bottom of this link
http://wiki.scipy.org/PerformancePython
From the introduction,

A comparison of weave with NumPy, Pyrex, Psyco, Fortran (77 and 90) and C++ for solving Laplace's equation.

It also compares MATLAB and seems to show similar speeds to when using Python and NumPy.
Of course this is only a specific example, your application might be allow better or worse performance. There is no harm in running the same test on both and comparing.
You can also compile NumPy with optimized libraries such as ATLAS which provides some BLAS/LAPACK routines. These should be of comparable speed to MATLAB. 
I'm not sure if the NumPy downloads are already built against it, but I think ATLAS will tune libraries to your system if you compile NumPy,
http://www.scipy.org/Installing_SciPy/Windows
The link has more details on what is required under the Windows platform.
EDIT:
If you want to find out what performs better, C or C++, it might be worth asking a new question. Although from the link above C++ has best performance. Other solutions are quite close too i.e. Pyrex, Python/Fortran (using f2py) and inline C++.
The only matrix algebra under C++ I have ever done was using MTL  and implementing an Extended Kalman Filter. I guess, though, in essence it depends on the libraries you are using LAPACK/BLAS and how well optimised it is. 
This link has a list of object-oriented numerical packages for many languages.
http://www.oonumerics.org/oon/

A:

NumPy and MATLAB both use an underlying BLAS implementation for standard linear algebra operations. For some time both used ATLAS, but nowadays MATLAB apparently also comes with other implementations like Intel's Math Kernel Library (MKL). Which one is faster by how much depends on the system and how the BLAS implementation was compiled. You can also compile NumPy with MKL and Enthought is working on MKL support for their Python distribution (see their roadmap). Here is also a recent interesting blog post about this.
On the other hand, if you need more specialized operations or data structures then both Python and MATLAB offer you various ways for optimization (like Cython, PyCUDA,...).
Edit: I corrected this answer to take into account different BLAS implementations. I hope it is now a fair representation of the current situation.

A:

The only valid test is to benchmark it.  It really depends on what your platform is, and how well the Biot-Savart Law maps to Matlab or NumPy/SciPy built-in operations.
As for making Python faster, Google's working on Unladen Swallow, a JIT compiler for Python.  There are probably other projects like this as well.

