With an array of IVec, you can create ICurve easily.

add_library('igeo')

size( 480, 360, IG.GL )

cpts1 = []

cpts1.append(IVec(-30, 10, 0))
cpts1.append(IVec(-10, 10, 0))
cpts1.append(IVec(-10, 30, 0))
cpts1.append(IVec(-30, 30, 0))
# curve 1 (red)
ICurve(cpts1, 3).clr(1.,0,0)


cpts2 = []
for i in range(10) :
    if i%2==0 :
        cpts2.append(IVec(i*10, 0, 0))
    else :
        cpts2.append(IVec(i*10, 10, 0))
# curve 2 (blue)
ICurve(cpts2, 1).clr(0,0,1.)

cpts3 = []
for i in range(16) :
    if i%4==0 :
        cpts3.append(IVec(-30, -10, i*5))
    elif i%4==1 :
        cpts3.append(IVec(-10, -10, i*5))
    elif i%4==2 :
        cpts3.append(IVec(-10, -30, i*5))
    else :
        cpts3.append(IVec(-30, -30, i*5)) # same with i%4==3
# curve 3 (cyan)
ICurve(cpts3, 3).clr(0,1.,1.)

2 dimensional array of IVec is convenient to create ISurface.

add_library('igeo')

size( 480, 360, IG.GL )

cpts1 = []
cpts1.append([])
cpts1[0].append(IVec( 0, 0, 0))
cpts1[0].append(IVec( 0,-30, 0))
cpts1.append([])
cpts1[1].append(IVec(-30, 0, 0))
cpts1[1].append(IVec(-30,-30, 0))
# surface 1 (gray)
ISurface(cpts1)

cpts2 = []
for i in range(10) : 
    cpts2.append([])
    if i%2==0 : 
        cpts2[i].append(IVec(i*10,0,0))
        cpts2[i].append(IVec(i*10,0,20))
    else : 
        cpts2[i].append(IVec(i*10,-10,0))
        cpts2[i].append(IVec(i*10,10,10))
# surface 2 (purple)
ISurface(cpts2).clr(.5,0,1)

cpts3 = []
for i in range(4) : 
    cpts3.append([])
    for j in range(4) : 
        if (i==0 or i==3) and (j==1 or j==2) :
            cpts3[i].append(IVec(-i*10, j*10, 20))
        else :
            cpts3[i].append(IVec(-i*10, j*10, 0))
# surface 3 (pink)
ISurface(cpts3,3,3).clr(1,.5,1)

One of ways to create a polygon mesh is to provide a matrix of IVec in 2 dimensional array.

add_library('igeo')

size( 480, 360, IG.GL )

cpts1 = []

for i in range(10) : 
    cpts1.append([])
    for j in range(10) : 
        if (i+j)%2==0 :
            cpts1[i].append(IVec(i*5, -j*5-30, (i+j)*2))
        else : 
            cpts1[i].append(IVec(i*5, -j*5-30, (i+j-1)*2))
# mesh 1 (cyan)
IMesh(cpts1).clr(0,1.,1.)

divNum=30
cpts2 = []
for i in range(10) : 
    cpts2.append([])
    for j in range(divNum+1) :
        radius = 30 - i*3
        angle = 2 * PI / divNum * j
        cpts2[i].append(IVec(cos(angle)*radius, sin(angle)*radius, i*i*.5))
# mesh 2 (red)
IMesh(cpts2).clr(1.,0,0)

Note that the use of constant PI to calculate the angle to be used in trigonometric function. divNum is dividing 2 * PI, not 360 because the unit of sin() and cos() is not degree but radian.
Please also note that the length of the array cpts2 in the second dimension is not divNum but divNum+1 to match points on the end edge with points on the start edge.