Adding tuples of lists to a list in python

Question

I don't understand the syntax of adding tuples whose elements are also elements of a list to another list that encompasses all of the information.

I'm trying to create a trajectory list that contains tuples of flight data of a projectile during flight. I want to use tuples so that I can see all of the information for each moment in time.

import random
import math

gg = -9.81 # gravity m/s**2
tt = 10 **-9 # seconds
wind = random.randint(-10,10)   # m/s

#position
x=random.randint(0,100)   # m/s

#projectile

v0 = float(raw_input('Enter the initial velocity (m/s) -> '));
theta = float(raw_input('Enter the initial launch angle of projectile (degrees) -> '));

theta *= (180/3.14159265359)

xx = [x]
yy = [.000000000000000000001]
dz =[v0]
time = [0];


data = ( time, xx, yy, dz)
traj = [data]


while yy[-1] >0:

    traj.append ( math.sqrt( (traj[-1][3][-1] * math.sin(theta) + gg * tt)** 2+        (traj[-1][4] * math.cos(theta) -wind) ** 2 ))    # velocity
    traj.append ( traj[-1][2][-1] + dz[-1] * math.sin(theta) * tt + .5* gg * tt)    # y position
    traj.append ( traj[-1][1][-1] * dz[-1] * math.cos(theta) - wind * tt)    # x position
    traj.append ( traj[-1][0][-1] + tt)     # time


print traj

Edit: I would input integers for the initial angle and velocity (ie-45,45). Expected outputs would be a list of tuples containing four elements corresponding to the time, x coordinate, y coordinate, and velocity, respectively. Currently, I'm receiving a tuple index out of range error.

Answer 1

Where you have

traj[-1][4]

in your first traj.append line, traj[-1] is data , and data is only four elements long, so the last item is at index 3.

Answer 2

The problem with your code is that you append data the values you compute in the while loop to the traj list. This will not update the lists xx , yy , time or dz . You could modify the code in the following way

while yy[-1] > 0:
    dz_next = math.sqrt( (yy[-1] * math.sin(theta) + gg * tt)** 2+(dz[-1] * math.cos(theta) -wind)** 2)
    yy_next = yy[-1] + dz[-1] * math.sin(theta) * tt + .5* gg * tt
    xx_next = xx[-1] * dz[-1] * math.cos(theta) - wind * tt

    dz.append(dz_next)    # velocity
    yy.append(yy_next)    # y position
    xx.append(xx_next)    # x position
    time.append(time[-1] + tt)     # time

I think a better way would be the following

data = ( 0, x, 1e-20, v0) # initial data
traj = [data]

while True:
    t, x, y, v = traj[-1]
    if y < 0:
        break

    traj.append((t + tt, # time
                 x * v * math.cos(theta) - wind * tt, # x position
                 y + v * math.sin(theta) * tt + .5* gg * tt, # y position
                 (y* math.sin(theta) + gg * tt)** 2 + (v*math.cos(theta) -wind) ** 2) # velocity
    )


    print traj
    t_traj, x_traj, y_traj, z_traj = zip(*traj)