Python: calling another python script

Question

Is it possible to call another python script to access just the definitions inside the script and nothing else?

In the script I want to import, there are plots that I want to suppress since there an not needed for this other program. That is, I only want to access the definitions of the Stumpff functions without plotting the figures.

The script I want to import is:

#!/usr/bin/env ipython
#  This program plots the Stumpff functions C(z) and S(z)

import numpy as np
import pylab
from matplotlib.ticker import MaxNLocator


def C(z):
    if z > 0:
        return (1 - np.cos(z ** 0.5)) / z
    elif z < 0:
        return (np.cosh(np.sqrt(-z)) - 1) / -z
    return 0.5


def S(z):
    if z > 0:
        return (np.sqrt(z) - np.sin(z ** 0.5)) / np.sqrt(z) ** 3
    elif z < 0:
        return (np.sinh(np.sqrt(-z)) - np.sqrt(-z)) / np.sqrt(-z) ** 3
    return 1.0 / 6.0


vC = np.vectorize(C)
vS = np.vectorize(S)

z = np.linspace(-50.0, 500.0, 100000.0)
y = vC(z)
y2 = vS(z)

fig = pylab.figure()
ax = fig.add_subplot(111)
ax.plot(z, y, 'r')
ax.plot(z, y2, 'b')
pylab.legend(('$C(z)$', '$S(z)$'), loc = 0)
pylab.xlim((-50, 0))
pylab.ylim((0, 12))
pylab.xlabel('$z$')
pylab.gca().xaxis.set_major_locator(MaxNLocator(prune = 'lower'))
pylab.savefig('stumpffneg50to0.eps', format = 'eps')


fig2 = pylab.figure()
ax2 = fig2.add_subplot(111)
ax2.plot(z, y, 'r')
ax2.plot(z, y2, 'b')
pylab.legend(('$C(z)$', '$S(z)$'), loc = 1)
pylab.xlim((0, 30))
pylab.ylim((0, 0.5))
pylab.xlabel('$z$')
pylab.gca().xaxis.set_major_locator(MaxNLocator(prune = 'lower'))
pylab.savefig('stumpff0to30.eps', format = 'eps')


fig3 = pylab.figure()
ax3 = fig3.add_subplot(111)
ax3.plot(z, y, 'r')
ax3.plot(z, y2, 'b')
pylab.legend(('$C(z)$', '$S(z)$'), loc = 0)
pylab.xlim((0, 500))
pylab.ylim((0, 0.05))
pylab.xlabel('$z$')
pylab.gca().xaxis.set_major_locator(MaxNLocator(prune = 'lower'))
pylab.savefig('stumpff0to500.eps', format = 'eps')
pylab.show()

From reading python how do I call external python programs, I see that I have add

import stumpff

After that, will my new script understand C(z) and S(z)?

Answer 1

The way your script is written, there is no way to import it and not have the plots made.

To make it so that import stumpff will work, and your script will understand C(z) and S(z), you'll need to make the plotting code such that it will only run if you are running as a script. One way to do this is to put all of it in a main() function, and then use

if __name__ == '__main__':
    main()

Alternatively, simply have all of it underneath that condition, like this:

#!/usr/bin/env ipython
#  This program plots the Stumpff functions C(z) and S(z)

import numpy as np
import pylab
from matplotlib.ticker import MaxNLocator


def C(z):
    if z > 0:
        return (1 - np.cos(z ** 0.5)) / z
    elif z < 0:
        return (np.cosh(np.sqrt(-z)) - 1) / -z
    return 0.5


def S(z):
    if z > 0:
        return (np.sqrt(z) - np.sin(z ** 0.5)) / np.sqrt(z) ** 3
    elif z < 0:
        return (np.sinh(np.sqrt(-z)) - np.sqrt(-z)) / np.sqrt(-z) ** 3
    return 1.0 / 6.0


if __name__ == '__main__':
    vC = np.vectorize(C)
    vS = np.vectorize(S)

    z = np.linspace(-50.0, 500.0, 100000.0)
    y = vC(z)
    y2 = vS(z)

    fig = pylab.figure()
    ax = fig.add_subplot(111)
    ax.plot(z, y, 'r')
    ax.plot(z, y2, 'b')
    pylab.legend(('$C(z)$', '$S(z)$'), loc = 0)
    pylab.xlim((-50, 0))
    pylab.ylim((0, 12))
    pylab.xlabel('$z$')
    pylab.gca().xaxis.set_major_locator(MaxNLocator(prune = 'lower'))
    pylab.savefig('stumpffneg50to0.eps', format = 'eps')


    fig2 = pylab.figure()
    ax2 = fig2.add_subplot(111)
    ax2.plot(z, y, 'r')
    ax2.plot(z, y2, 'b')
    pylab.legend(('$C(z)$', '$S(z)$'), loc = 1)
    pylab.xlim((0, 30))
    pylab.ylim((0, 0.5))
    pylab.xlabel('$z$')
    pylab.gca().xaxis.set_major_locator(MaxNLocator(prune = 'lower'))
    pylab.savefig('stumpff0to30.eps', format = 'eps')


    fig3 = pylab.figure()
    ax3 = fig3.add_subplot(111)
    ax3.plot(z, y, 'r')
    ax3.plot(z, y2, 'b')
    pylab.legend(('$C(z)$', '$S(z)$'), loc = 0)
    pylab.xlim((0, 500))
    pylab.ylim((0, 0.05))
    pylab.xlabel('$z$')
    pylab.gca().xaxis.set_major_locator(MaxNLocator(prune = 'lower'))
    pylab.savefig('stumpff0to500.eps', format = 'eps')
    pylab.show()

Then, you can use import stumpff, and you can use stumpff.C(z) and stumpff.S(z). If you want to be able to use them without stumpff before them, then use from stumpff import *, or from stumpff import C, S