bin/wkt_n-gon

   1 #!/usr/bin/python
   2
   3 """
   4 Output the Well-Known-Text[1] representation of an n-gon, centered at
   5 (0,0).
   6
   7 The parameter n is passed as a required command-line option. The
   8 radius of the n-gon is an optional argument.
   9
  10 [1] http://en.wikipedia.org/wiki/Well-known_text
  11 """
  12
  13 import math
  14 import site
  15 import sys
  16 from optparse import OptionParser
  17 import os
  18
  19 # Basically, add '../src' to our path.
  20 # Needed for the imports that follow.
  21 site.addsitedir(os.path.dirname(os.path.abspath(sys.argv[0])) + '/../src')
  22
  23 import CLI
  24 import ExitCodes
  25 import Geometry
  26 import StringUtils
  27
  28 usage = '%prog [options] <number of sides>'
  29 fmtr = CLI.VerbatimHelpFormatter()
  30 parser = OptionParser(usage, formatter=fmtr)
  31
  32 # Use this module's docstring as the description.
  33 parser.description = __doc__
  34
  35
  36 parser.add_option('-r',
  37                   '--radius',
  38                   type="float",
  39                   help="The radius of the n-gon. Defaults to 1.0.",
  40                   default=1.0)
  41
  42
  43 (options, args) = parser.parse_args()
  44
  45 if (len(args) < 1) or (not StringUtils.is_integer(args[0])):
  46     print "\nERROR: You must supply the number of sides, n.\n"
  47     parser.print_help()
  48     print '' # Print a newline.
  49     raise SystemExit(ExitCodes.NOT_ENOUGH_ARGS)
  50
  51 # The conversion of n to int is safe, since it passed is_integer
  52 # above.
  53 n = int(args[0])
  54 r = options.radius
  55
  56 # Each new coordinate is going to be separated from the previous by
  57 # angle_delta radians.
  58 angle_delta = 2*math.pi / float(n)
  59
  60 # The set of coordinates, as two-tuples. We already know the first
  61 # one--it's just cos/sin of 0.
  62 coords = [(r, 0)]
  63
  64 for coord_idx in range(1, n):
  65     angle = coord_idx * angle_delta
  66     x = r * math.cos(angle)
  67     y = r * math.sin(angle)
  68     coords.append((x, y))
  69
  70 # A well-known-text polygon must be closed, i.e. the last coordinate
  71 # must equal the first. So, we're missing a coordinate, but the
  72 # Polygon class will handle it for us.
  73 p = Geometry.Polygon(coords)
  74 print p.wkt()