Python: How can I call a variable when using an eval function?

Question

I am trying to create a really simple Python program where I can input a planet by its name and have the approximate distance stated. Currently, I have the seven planets listed and equal to their distances right below that eval function.

This is what the code looks like currently:

def = def Planet_Calculations():
    Planet = exec(input("What planet are you trying to calculate the distance for? (Note: Pluto is no longer a planet!) "))
    Mercury = 56,974,146
    Venus = 25,724,767 
    Earth = 0 
    Mars = 48,678,219
    Jupiter = 390,674,710
    Saturn = 792,248,270
    Uranus = 1,692,662,530
    Neptune = 2,703,959,960

print("The distance to the specified planet is approxametly:" , Planet, "million miles from Earth." )

Planet_Calculations()

When I try to type in a planet such as "Mars" into the eval, I have no idea how to actually have the program input its distance into the print function further down. I would greatly appreciate any type of feedback or help.

Padraic Cunningham · Accepted Answer · 2016-09-10 23:05:14Z

1

Use a dict mapping planets to the tuples::

def planet_calculations():
    planet = input("What planet are you trying to calculate the distance for? (Note: Pluto is no longer a planet!) ")
    planets = {'Mercury': (56, 974, 146), 'Neptune': (2, 703, 959, 960), 'Jupiter': (390, 674, 710),
               'Uranus': (1, 692, 662, 530),
               'Mars': (48, 678, 219), 'Earth': 0, 'Venus': (25, 724, 767), 'Saturn': (792, 248, 270)}
    print("The distance to the specified planet is approxametly: {} million miles from Earth."
          .format(planets[planet])

If you want the output like "56,974,146" store the values as strings and not tuples.

Also if you want to use the value outside the function, you need to return it:

def planet_calculations():
    planet = input("What planet are you trying to calculate the distance for? (Note: Pluto is no longer a planet!) ")
    planets = {'Mercury': (56, 974, 146), 'Neptune': (2, 703, 959, 960), 'Jupiter': (390, 674, 710),
               'Uranus': (1, 692, 662, 530),
               'Mars': (48, 678, 219), 'Earth': 0, 'Venus': (25, 724, 767), 'Saturn': (792, 248, 270)}
    return planets[planet]
print("The distance to the specified planet is approxametly: {} million miles from Earth."
        .format(planet_calculations()))

edited Sep 10, 2016 at 23:05

answered Sep 10, 2016 at 22:59

Padraic Cunningham

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1 Comment

GottaLoveArchery Over a year ago

Thank you for your help Padraic!

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