Generate svg grids

grid.py

import sys
from svg import *

def log(*a, **k):
    print(*a, **k, file=sys.stderr)

GRID = int(sys.argv[1]) if len(sys.argv) > 1 else 6

GAP = 20

# Basic header
svg_header()
svg_open(width=8*GAP*(GRID+2), height=8*GAP*(GRID+2), x_bias=0, y_bias=0,
         xw=GAP*(GRID+2), yh=GAP*(GRID+2))

for x in range(1, GRID + 2):
    svg_line((GAP*x, 1), (GAP*x, GAP*(GRID + 1)+GAP-1), stroke='black')

for y in range(1, GRID + 2):
    svg_line((1, GAP*y), (GAP*(GRID+1)+GAP-1, GAP*y), stroke='black')

# Footer
svg_close()

Makefile

.PHONY: test
test: grid6.svg grid7.svg grid8.svg grid9.svg grid6.png grid7.png grid8.png grid9.png

grid%.svg: grid.py
	python3 $^ $* > $@

%.png: %.svg
	convert $^ $@

.PHONY: clean
clean:
	rm -f *.png *.svg

svg.py

def xml(tag, _xml_tag_is_a_singleton=True, **options):
    s = f'<{tag}'
    kw_attrib = lambda x: x.replace('_', '-')
    if options:
        s += ' '
        s += ' '.join(f'{kw_attrib(k)}="{str(v)}"' for k, v in options.items())
    if _xml_tag_is_a_singleton:
        s += ' />'
    else:
        s += '>'
    print(s)

def xml_open(*args, **kwargs):
    xml(*args, **kwargs, _xml_tag_is_a_singleton=False)

def xml_close(tag):
    print(f'</{tag}>')

def svg_header():
    '<?xml version="1.0" encoding="UTF-8" standalone="no"?>'

def svg_open(width, height, x_bias, y_bias, xw, yh):
    vb = f'{x_bias} {y_bias} {xw} {yh}'
    ns = 'http://www.w3.org/2000/svg'
    xml_open('svg', width=width, height=height, viewBox=vb, xmlns=ns)

def svg_close():
    xml_close('svg')

def svg_poly(*points, **opts):
    point_str = ' '.join(f'{x},{y}' for x, y in points)
    xml('polyline', points=point_str, **opts)

def svg_circle(point, radius, **opts):
    xml('circle', cx=point[0], cy=point[1], r=radius, **opts)

def svg_line(p1, p2, **opts):
    xml('line', x1=p1[0], y1=p1[1], x2=p2[0], y2=p2[1], **opts)

def svg_rect(p, width, height, x_radius=0, y_radius=0, **opts):
    xml('rect', x=p[0], y=p[1], width=width, height=height,
              rx=x_radius, ry=y_radius, **opts)