Return to Answer

from mathutils import Vector, Matrix
from mathutils.noise import random, seed_set
import bpy

# Specify parameters
seed = 0
xmin = -10
xmax = 10
ymin = -10
ymax = 10
radius = 1
num_circles = 68
max_tries = 10000
max_height = 4
# Init
seed_set(seed)
sx = xmax - xmin - 2 * radius
sy = ymax - ymin - 2 * radius
xminm = xmin + radius
yminm = ymin + radius
existing_locations = []
sce = bpy.context.scene
bpy.ops.mesh.primitive_cylinder_add(
    location=(0, 0, 0),
    depth=1,
    radius=radius)
ref_circle = bpy.context.object
ref_circle.data.transform(Matrix.Translation((0, 0, 0.5)))

# Loop
for i in range(num_circles):
    j = 0
    searchOn = True
    while searchOn:
        if j > max_tries: 
            print("Placed", i, "of", num_circles)
            bpy.ops.object.select_all(action='DESELECT')
            ref_circle.select_set(True)
            bpy.ops.object.delete()
            raise ValueError('Found no more room for another circle')
            break
        j += 1
        new_location = (xminm + random() * sx,
                        yminm + random() * sy,
                        0)
        for existing_location in existing_locations:
            if (Vector(existing_location) - Vector(new_location)).length < 2 * radius:
                break
        else:
            new_circle = ref_circle.copy()
            new_circle.dimensions.z = max_height * random()
            new_circle.location = new_location
            sce.collection.objects.link(new_circle)
            existing_locations.append(new_location)
            searchOn = False

ref_circle.select_set(True)
bpy.ops.object.delete()
sce.update()

from mathutils import Vector, Matrix
from mathutils.noise import random, seed_set
import bpy

# Specify parameters
seed = 0
xmin = -10
xmax = 10
ymin = -10
ymax = 10
radius = 1
num_circles = 68
max_tries = 10000
max_height = 4
# Init
seed_set(seed)
sx = xmax - xmin - 2 * radius
sy = ymax - ymin - 2 * radius
xminm = xmin + radius
yminm = ymin + radius
existing_locations = []
sce = bpy.context.scene
bpy.ops.mesh.primitive_cylinder_add(
    location=(0, 0, 0),
    depth=1,
    radius=radius)
ref_circle = bpy.context.object
ref_circle.data.transform(Matrix.Translation((0, 0, 0.5)))

# Loop
for i in range(num_circles):
    j = 0
    searchOn = True
    while searchOn:
        if j > max_tries: 
            print("Placed", i, "of", num_circles)
            bpy.ops.object.select_all(action='DESELECT')
            ref_circle.select_set(True)
            bpy.ops.object.delete()
            raise ValueError('Found no more room for another circle')
            break
        j += 1
        new_location = (xminm + random() * sx,
                        yminm + random() * sy,
                        0)
        for existing_location in existing_locations:
            if (Vector(existing_location) - Vector(new_location)).length < 2 * radius:
                break
        else:
            new_circle = ref_circle.copy()
            new_circle.dimensions.z = max_height * random()
            new_circle.location = new_location
            sce.collection.objects.link(new_circle)
            existing_locations.append(new_location)
            searchOn = False

ref_circle.select_set(True)
bpy.ops.object.delete()
context.view_layer.update()

Test run, settings as posted

from mathutils import Vector, Matrix
from mathutils.noise import random, seed_set
import bpy

# Specify parameters
seed = 0
xmin = -10
xmax = 10
ymin = -10
ymax = 10
radius = 1
num_circles = 68
max_tries = 10000
max_height = 4
# Init
seed_set(seed)
sx = xmax - xmin - 2 * radius
sy = ymax - ymin - 2 * radius
xminm = xmin + radius
yminm = ymin + radius
existing_locations = []
sce = bpy.context.scene
bpy.ops.mesh.primitive_cylinder_add(
    location=(0, 0, 0),
    depth=1,
    radius=radius)
ref_circle = bpy.context.object
ref_circle.data.transform(Matrix.Translation((0, 0, 0.5)))

# Loop
for i in range(num_circles):
    j = 0
    searchOn = True
    while searchOn:
        if j > max_tries:
            bpy.ops.object.select_all(action='DESELECT')
            ref_circle.select_set(True)
            bpy.ops.object.delete()
            raise ValueError('Found no more room for another circle')
            break
        j += 1
        new_location = (xminm + random() * sx,
                        yminm + random() * sy,
                        0)
        for existing_location in existing_locations:
            if (Vector(existing_location) - Vector(new_location)).length < 2 * radius:
                break
        else:
            new_circle = ref_circle.copy()
            new_circle.dimensions.z = max_height * random()
            new_circle.location = new_location
            sce.collection.objects.link(new_circle)
            existing_locations.append(new_location)
            searchOn = False

ref_circle.select_set(True)
bpy.ops.object.delete()
sce.update()

Test run, settings as posted Placed 66 of 68

from mathutils import Vector, Matrix
from mathutils.noise import random, seed_set
import bpy

# Specify parameters
seed = 0
xmin = -10
xmax = 10
ymin = -10
ymax = 10
radius = 1
num_circles = 68
max_tries = 10000
max_height = 4
# Init
seed_set(seed)
sx = xmax - xmin - 2 * radius
sy = ymax - ymin - 2 * radius
xminm = xmin + radius
yminm = ymin + radius
existing_locations = []
sce = bpy.context.scene
bpy.ops.mesh.primitive_cylinder_add(
    location=(0, 0, 0),
    depth=1,
    radius=radius)
ref_circle = bpy.context.object
ref_circle.data.transform(Matrix.Translation((0, 0, 0.5)))

# Loop
for i in range(num_circles):
    j = 0
    searchOn = True
    while searchOn:
        if j > max_tries: 
            print("Placed", i, "of", num_circles)
            bpy.ops.object.select_all(action='DESELECT')
            ref_circle.select_set(True)
            bpy.ops.object.delete()
            raise ValueError('Found no more room for another circle')
            break
        j += 1
        new_location = (xminm + random() * sx,
                        yminm + random() * sy,
                        0)
        for existing_location in existing_locations:
            if (Vector(existing_location) - Vector(new_location)).length < 2 * radius:
                break
        else:
            new_circle = ref_circle.copy()
            new_circle.dimensions.z = max_height * random()
            new_circle.location = new_location
            sce.collection.objects.link(new_circle)
            existing_locations.append(new_location)
            searchOn = False

ref_circle.select_set(True)
bpy.ops.object.delete()
sce.update()

from mathutils import Vector, Matrix
from mathutils.noise import random, seed_set
import bpy

# Specify parameters
seed = 0
xmin = -10
xmax = 10
ymin = -10
ymax = 10
radius = 1
num_circles = 68
max_tries = 10000
max_height = 4
# Init
seed_set(seed)
sx = xmax-xmin-2*radius
sy = ymax-ymin-2*radius
xminm = xmin+radius 
yminm = ymin+radius 
existing_locations = []
sce = bpy.context.scene
bpy.ops.mesh.primitive_cylinder_add(
        location=(0,0,0), 
        depth=1,
        radius=radius)
ref_circle = bpy.context.object
ref_circle.data.transform(Matrix.Translation((0, 0, 0.5)))

# Loop
for i in range(num_circles):
    j = 0
    searchOn = True
    while searchOn:
        if j > max_tries:
            bpy.ops.object.select_all(action='DESELECT')
            ref_circle.select_set(True)
            bpy.ops.object.delete() 
            raise ValueError('Found no more room for another circle')
            break
        j += 1
        new_location = (xminm + random()*sx,
                        yminm + random()*sy,
                        0)
        for existing_location in existing_locations:
            if (Vector(existing_location)-Vector(new_location)).length < 2*radius:
                break
        else:
            new_circle = ref_circle.copy()
            new_circle.dimensions.z = max_height * random()
            new_circle.location = new_location
            sce.collection.objects.link(new_circle)
            existing_locations.append(new_location)
            searchOn = False

ref_circle.select_set(True)
bpy.ops.object.delete() 
sce.update()

from mathutils import Vector, Matrix
from mathutils.noise import random, seed_set
import bpy

# Specify parameters
seed = 0
xmin = -10
xmax = 10
ymin = -10
ymax = 10
radius = 1
num_circles = 68
max_tries = 10000
max_height = 4
# Init
seed_set(seed)
sx = xmax - xmin - 2 * radius
sy = ymax - ymin - 2 * radius
xminm = xmin + radius
yminm = ymin + radius
existing_locations = []
sce = bpy.context.scene
bpy.ops.mesh.primitive_cylinder_add(
    location=(0, 0, 0),
    depth=1,
    radius=radius)
ref_circle = bpy.context.object
ref_circle.data.transform(Matrix.Translation((0, 0, 0.5)))

# Loop
for i in range(num_circles):
    j = 0
    searchOn = True
    while searchOn:
        if j > max_tries:
            bpy.ops.object.select_all(action='DESELECT')
            ref_circle.select_set(True)
            bpy.ops.object.delete()
            raise ValueError('Found no more room for another circle')
            break
        j += 1
        new_location = (xminm + random() * sx,
                        yminm + random() * sy,
                        0)
        for existing_location in existing_locations:
            if (Vector(existing_location) - Vector(new_location)).length < 2 * radius:
                break
        else:
            new_circle = ref_circle.copy()
            new_circle.dimensions.z = max_height * random()
            new_circle.location = new_location
            sce.collection.objects.link(new_circle)
            existing_locations.append(new_location)
            searchOn = False

ref_circle.select_set(True)
bpy.ops.object.delete()
sce.update()