# why the difference between ipython and python shell?

Charles R Harris charlesr.harris at gmail.com
Mon Nov 13 13:13:07 CST 2006

On 11/13/06, Seweryn Kokot <skokot at po.opole.pl> wrote:
>
> Hello,
>
> Why ipython and python interactive shell give two different information?
>
> --- ipython
> Python 2.4.4 (#2, Oct 20 2006, 00:23:25)
>
> IPython 0.7.2 -- An enhanced Interactive Python.
> ?       -> Introduction to IPython's features.
> %magic  -> Information about IPython's 'magic' % functions.
> help    -> Python's own help system.
> object? -> Details about 'object'. ?object also works, ?? prints more.
>
> In [1]: from scipy import linalg
>
> In [2]: help(linalg.eig)
>
> Help on function eig in module numpy.linalg.linalg:
>
> eig(a)
>     eig(a) returns u,v  where u is the eigenvalues and
>     v is a matrix of eigenvectors with vector v[:,i] corresponds to
>     eigenvalue u[i].  Satisfies the equation dot(a, v[:,i]) =
>     u[i]*v[:,i]
> --- ipython
>
> while
>
> --- python
> Python 2.4.4 (#2, Oct 20 2006, 00:23:25)
> [GCC 4.1.2 20061015 (prerelease) (Debian 4.1.1-16.1)] on linux2
> >>> from scipy import linalg
> >>> help(linalg.eig)
>
> Help on function eig in module scipy.linalg.decomp:
>
> eig(a, b=None, left=False, right=True, overwrite_a=False,
> overwrite_b=False)
>     Solve ordinary and generalized eigenvalue problem
>     of a square matrix.
>
>     Inputs:
>
>       a     -- An N x N matrix.
>       b     -- An N x N matrix [default is identity(N)].
>       left  -- Return left eigenvectors [disabled].
>       right -- Return right eigenvectors [enabled].
>       overwrite_a, overwrite_b -- save space by overwriting the a and/or
>                                   b matrices (both False by default)
>
>     Outputs:
>
>       w      -- eigenvalues [left==right==False].
>       w,vr   -- w and right eigenvectors [left==False,right=True].
>       w,vl   -- w and left eigenvectors [left==True,right==False].
>       w,vl,vr  -- [left==right==True].
>
>     Definitions:
> ...
> --- python
>
> Any idea?

I expect scipy.linalg and numpy.linalg are different modules containing
different functions. That said, the documentation in scipy.linalg looks
quite a bit more complete.

Chuck
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