Can anyone help with a python 3 question?

# Constant
pi=3.14

# Initialize lists
radiuses=[0.5,1,1.5,2,2.5,3,3.5,4] # Just FYI, the correct plural form is "radii."
volume=[]
surface_area=[]

# Calculate volumes and surface areas
for rad in radiuses:
volume += [4/3 * pi * rad**3]
surface_area += [4 * pi * rad**2]
# Print surface areas
print (surface_area)

# Initialize ratio list
ratios= []

# For i in range [0,8), calculate the value of surface_area[i] / volume[i], round to two decimal places, and add it to the end of the ratio list.
# SUGGESTION: Consider changing the "8" to "len(radiuses)" so that you only have to change one thing
# if you decide to make "radiuses" longer or shorter.
for number in range(8):
ratio = round(surface_area[number] / volume[number],2)
ratios.append (ratio)

# Print the ratio list (assuming you want to do this)
print(ratios)

Mayling said:

I'm trying to create an empty list using a for-loop that calculates the ratio for the different radiuses, and adds it to the empty list.


from pylab import *

pi=3.14
radiuses=[0.5,1,1.5,2,2.5,3,3.5,4]
volume = 4/3 * pi * radiuses**3
surface_area = 4 * pi * radiuses**2
print (surface_area)

ratios= []


for number in range(8)
ratio = round(surface_area / volume,2)
ratios.append (number)

#!/usr/bin/env python
import math

radius = [0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4]
result = []

def findratio(x):
    return round((4 * math.pi * x**2) / (4 / 3 * math.pi * x**3), 2) #kinda ugly

for i in radius:
    result.append(findratio(i))

print(result)

$ ./spherething.py
[6.0, 3.0, 2.0, 1.5, 1.2, 1.0, 0.86, 0.75]

Zuggy said:

ratios = [] is the correct way to create an empty list, only you're filling it with the iterator from the for loop instead of the ratio variable.

Here's a shorter way you could write this:


Running the program:

Phendrus said:
I don't have pylab handy and I don't feel like redownloading it, so I can't comment on whether you're using its (list * int -> list) operators correctly. However, assuming you have those right and you're indenting properly, your only mistake is that you forgot to put a colon on the end of the for statement.

Also, you probably meant to append "ratio" to ratios, rather than "number".

Without using pylab's list operators, I believe this is what you're looking for (indent where appropriate, since MAL apparently doesn't like leading spaces):


Edit: Closed off code in a quote box and added comments.