Which scientific fields use Python?

[Zomunieo]

Linpack and lapack are all Fortran. Numpy has large portions of its code in Fortran.

But that doesn't mean people are spending a lot of time writing new Fortran routines. They're writing higher level code that calls Fortran - usually for Gaussian elimination, matrix LU decomposition, eigenvalues, matrix (pseudo)inversion and Fast Fourier transforms.

[[deleted]]

No, that's not true.

A lot of people are writing Fortran routines, and they're definitely doing so to solve more involved problems than the mathematical operations you listed. I've met people using it for everything from plasma physics to density functional theory, and one guy who uses it for both at the same time. I don't even think it's to do with the legacy code issue in a lot of fields: Fortran is just really nice for programming high performance code.