python3 recursive correctness for my function

Question

I need help on a problem. For example I have the following dictionary named planets:

{'Mercury': {'Orbital Radius': '38001200', 'Radius': '243900.7',
'Period': '87.9691'}, 'Ariel': {'Orbital Radius': '8595000', 'Radius':
'60000', 'Period': '2.520379'}, 'Sun': {'Satellites':
'Mercury,Venus,Earth,Mars,Jupiter,Saturn,Uranus,Neptune,Ceres,Pluto,Haumea,Makemake,Eris',
'Orbital Radius': '0', 'Radius': '20890260'}, 'Phobos': {'Orbital
Radius': '3623500.6', 'Radius': '200000', 'Period': '0.31891023'},
'Deimos': {'Orbital Radius': '8346000', 'Radius': '200000.2',
'Period': '1.26244'}, 'Mars': {'Satellites': 'Phobos,Deimos', 'Orbital
Radius': '106669000', 'Radius': '339600.2', 'Period': '686.971'},
'Rhea': {'Orbital Radius': '24000000', 'Radius': '75000', 'Period':
'4.5'}, 'Oberon': {'Orbital Radius': '26235000', 'Radius': '75000',
'Period': '13.463'}, 'Europa': {'Orbital Radius': '36486200',
'Radius': '156000.8', 'Period': '3.551181'}, 'Tethys': {'Orbital
Radius': '13706000', 'Radius': '50000', 'Period': '1.9'}, 'Miranda':
{'Orbital Radius': '5822550', 'Radius': '23500', 'Period': '1.413'},
'Saturn': {'Satellites':
'Mimas,Enceladus,Tethys,Dione,Rhea,Titan,Iapetus', 'Orbital Radius':
'353572956', 'Radius': '6026800', 'Period': '10759.22'}, 'Uranus':
{'Satellites': 'Puck,Miranda,Ariel,Umbriel,Titania,Oberon', 'Orbital
Radius': '453572956', 'Radius': '2555900', 'Period': '30799'},
'Neptune': {'Satellites': 'Triton', 'Orbital Radius': '550000000',
'Radius': '2476400', 'Period': '60190'}, 'Titania': {'Orbital Radius':
'19575000', 'Radius': '75000', 'Period': '8.7058'}, 'Enceladus':
{'Orbital Radius': '10706000', 'Radius': '25000', 'Period': '1.4'},
'Venus': {'Orbital Radius': '57477000', 'Radius': '605100.8',
'Period': '224.698'}, 'Moon': {'Orbital Radius': '18128500', 'Radius':
'173700.10', 'Period': '27.321582'}, 'Triton': {'Orbital Radius':
'40000000', 'Radius': '135300', 'Period': '-5.8'}, 'Ceres': {'Orbital
Radius': '130995855', 'Radius': '48700', 'Period': '1679.67'},
'Mimas': {'Orbital Radius': '8433396', 'Radius': '20600', 'Period':
'0.9'}, 'Titan': {'Orbital Radius': '50706000', 'Radius': '257600',
'Period': '15.945'}, 'Ganymede': {'Orbital Radius': '47160000',
'Radius': '263400', 'Period': '7.15455296'}, 'Umbriel': {'Orbital
Radius': '11983500', 'Radius': '60000', 'Period': '4.144177'},
'Callisto': {'Orbital Radius': '69700000', 'Radius': '241000',
'Period': '16.6890184'}, 'Jupiter': {'Satellites':
'Io,Europa,Ganymede,Callisto', 'Orbital Radius': '210573600',
'Radius': '7149200', 'Period': '4332.59'}, 'Io': {'Orbital Radius':
'22000000', 'Radius': '182100.3', 'Period': '1.7691377186'}, 'Earth':
{'Satellites': 'Moon', 'Orbital Radius': '77098290', 'Radius':
'637100.0', 'Period': '365.256363004'}, 'Dione': {'Orbital Radius':
'17106000', 'Radius': '56000', 'Period': '2.7'}, 'Iapetus': {'Orbital
Radius': '72285891', 'Radius': '75000', 'Period': '79'}}

and this is my code for a solar animation. My question is that does my code continually go and check every 'Object' for 'Satellites' and then print them if they exist? is it recursive? I've been working hard all day to make it check and then print!

#code for solar animation
#t = period
#x,y = rootobject coordinates

print("flush false")
scale = 600/max([planets[key]['Orbital Radius'] for key in planets])
t = 0
x = 400
y = 300
print("fillcircle",400,300,planets['Sun']['Radius']*scale)
print("text ", "\"Sun\"",x + planets['Sun']['Radius']*scale,y)


def satellites(planets):
    for 'Satellites' in planets:
        if 'Satellites' not in 'Object':
            return
        else:
            print("refresh")
            print("colour 0 0 0")
            print("clear")
            print("colour 255 255 255")
            r_sat = planets['Object']['Satellites']['Orbital Radius']*scale
            print("circle",x,y,r_sat)
            r_satX = x + math.sin(t*2*math.pi/planets['Object']['Satellites']['Period'])*r_sat
            r_satY = y + math.cos(t*2*math.pi/planets['Object']['Satellites']['Period'])*r_sat
            print("fillcircle",r_satX,r_satY,planets['Object']['Satellites']['Radius']*scale)
            print("text ",['Object']['Satellites'],r_satX + planets['Object']['Satellites']['Radius']*scale,r_satY)
            t += 0.02

system = satellites(planets)
print(system)

I am nearing my limits for this, I've tried everything I can think of but I need help!

You are using string literals instead of variable names: it should be `for satellites in planets` and `if satellites not in Object`. Didn't read the rest, good luck :) — Lev Levitsky, Nov 25 '12 at 12:30

score 2 · Accepted Answer · edited May 23 '17 at 12:12

1. My question is that does my code continually go and check every 'Object' for 'Satellites' and then print them if they exist?

No, your function satellites() it isn't valid python. That are quite a few mistakes with it but I can see you are heading in the right direction, sort of.

for 'Satellites' in planets:
    if 'Satellites' not in 'Object':
        return

'Satellites' is just a string so for 'string' in 'iterable object' isn't valid python.

if 'Satellites' not in 'Object': has the same problem as the previous line, the string 'Satellites' will never be in the string 'Object'

I believe this is what you wanted to do:

for key in planets.keys():               # For all keys in the outer dic 
    if 'Satellites' not in planets[key]: # Does inner dic have key 'Satellites'
        return

Where key is the variable (not a string) that takes each value contained in planets once round the loop. So the first time the value of key is 'Mecury', the second time the value of key is 'Sun' and so on.. We then look at the inner dictionary planets[key] and check if that dictionary has the key 'Satellites'.

Then uses planets[key]['Satellites'] not planets['Object']['Satellites'] as the key 'Object' never exists (look at the input file).

2. Is it recursive?

No, Your function satellites() never calls itselfs, re-read my answer on recursion: python3 recursion animation in QuickDraw

Yes that is what I was trying to get ! Thanks for clearing it up! I read it many times. Does that mean my 'if satellites not in planets[key]:' isn't the base case? — Romulus, Nov 25 '12 at 17:17
You are on the right track, If there are no `Satellites` left to print then return. — Chris Seymour, Nov 25 '12 at 17:19

python3 recursive correctness for my function

1 Answers1