On 09/14/2011 09:17 AM, Raymond Hawkins wrote:
> I'm getting odd behavior when I try to use fmin and pylab in the same
> program. The issue is illustrated in the code snippet below. As written, fmin
> won't work: the "print xopt" simply returns the contents of x0 as assigned in
> the line before fmin. If the "from pylab import *" line is commented out,
> however, then fmin runs as expected.
>
This is a good illustration of why "from package_x import *" is so
strongly discouraged; it is throwing away one of the most important
features of python--the default separation of packages into their own
name spaces.
The only exception with respect to pylab is that for quick and dirty
interactive use, particularly within ipython, it is sometimes worthwhile
to sacrifice some name space separation for typing speed. But in a
script that imports from more than one external package, it is best to
always use explicit imports in some form.
The preferred idiom is to avoid importing pylab at all in scripts;
instead, do this:
import numpy as np
import matplotlib.pyplot as plt
Eric
> I'm running python 2.7.2 on a MacBook Pro with a recent install& upgrade of
> scipy and matplotlib via macports. Any suggestions would be appreciated.
>
> -------------------------------------
>
> #!/opt/local/bin/python
>
> from scipy import *
> from scipy.optimize import fmin
> import matplotlib
> matplotlib.use('MacOSX')
> from pylab import *
>
> def rosen(x): # The Rosenbrock function
> return sum(100.0*(x[1:]-x[:-1]**2.0)**2.0 + (1-x[:-1])**2.0)
>
> x0 = [1.3, 0.7, 0.8, 1.9, 1.2]
>
> xopt = fmin(rosen, x0)
>
> print xopt
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