运行VPython代码时，“属性'pos‘必须是一个向量”错误

Question

当我运行这段代码时，我会得到一个错误" error : Property‘pos“必须是一个向量。我必须在某个地方写另一个向量吗？因为我把向量写在

grav_force = vector(0,-object.mass*grav_field,0)

这是我的全部密码

GlowScript 2.7 VPython

from visual import *

display(width = 1300, height = 1000)

projectile = sphere(pos = (-5,0,0),
                    radius = 0.1,
                    color = color.red,
                    make_trail = True)

projectile.speed = 3.2 # Initial speed.
projectile.angle = 75*3.141459/180 # Initial angle, from the +x-axis.

projectile.velocity = vector(projectile.speed*cos(projectile.angle),
                             projectile.speed*sin(projectile.angle),
                             0)

projectile.mass = 1.0
grav_field = 1.0

dt = 0.01
time = 0

while (projectile.pos.y >=0):
    rate(100)

    # Calculate the force.
    grav_force = vector(0,-projectile.mass*grav_field,0)

    force = grav_force

    # Update velocity.
    projectile.velocity = projectile.velocity + force/projectile.mass * dt

    # Update position.
    projectile.pos = projectile.pos + projectile.velocity * dt

    # Update time.
    time = time + dt

Answer 1

变化

projectile = sphere(pos = (-5,0,0), radius = 0.1,color = color.red, make_trail = True)

至

projectile = sphere(pos = vector(-5,0,0), radius = 0.1, color = color.red, make_trail = True)

见文件

http://www.glowscript.org/docs/VPythonDocs/sphere.html

也来自文件

GlowScript VPython和VPython 7与经典VPython 6的区别

向量必须表示为向量(x，y，z)或vec(x，y，z)，而不是表示为(x，y，z)。