CODEWITHSUNDEEP
pythonlisttuples
youngpadwan
youngpadwan

Reputation: 31

Adding tuples of lists to a list in python

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 (i.e.-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.

Upvotes: 0

Views: 123

Answers (2)

wasserfeder
wasserfeder

Reputation: 486

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)

Upvotes: 0

khelwood
khelwood

Reputation: 59232

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.

Upvotes: 1

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