Re: Error occur when running

[Bruce Sherwood]

I don't know what causes this error (maybe a Jupyter expert can comment), but I've always found that the cure is simply to replot the page (or maybe just restart the kernel). Have you tried this?

[Aaron Titus]

This error does not seem to affect running the vpython program or running the rest of the notebook. I see this error regularly, especially when creating a presentation that has many vpython programs in the same notebook. I do not know what causes the error. I also am not sure whether it is related to vpython or not.

A Google search on the error goes back to this ipython post from 2011.

https://github.com/ipython/ipython/pull/329/commits/7d1bdfaff74a040b88d1726b47ced673f227bed1

In summary, the “error” is may be annoying but not fatal.

AT

On Jun 7, 2017, at 1:55 AM, Lonan S. <sf.l...@gmail.com> wrote:

Hello, I am learning how to code and use vpython and then I got this error from running this code with Jupyter notebook. Is there any way to solve this problem?

ERROR! Session/line number was not unique in database. History logging moved to new session 88

. . .

from vpython import *
from math import *
canvas(width=900,height=900)
proj = sphere(pos = vector(-5,0,0),
             radius = 0.1,
             color = color.red,
             make_trail=True)
#velocity vector components
proj.speed = 10.0 #initial speed
proj.angle = 45*3.141459/180 #initial angle from the x+ axis
#velocity vector
proj.velocity = vector(proj.speed*cos(proj.angle),
                       proj.speed*sin(proj.angle),
                       0)
proj.mass = 1.0
grav_field = 9.8

#time
dt = 0.01
time =0

#loop
while(proj.pos.y >= 0):
    rate(10)
    #force(s)
    grav_force = vector(0,-proj.mass*grav_field,0)
   
    #Total force
    force = grav_force
   
    #Update Velocity
    proj.velocity += force/proj.mass * dt
   
    #Update Position
    proj.pos += proj.velocity * dt
   
    #Update Time
    time += dt

Thanks for your answer.

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