sun_position/geo.py

   1 #!/usr/bin/env python
   2 #
   3 # geo.py is a python module with no dependencies on extra packages,
   4 # providing some convenience functions for working with geographic
   5 # coordinates
   6 #
   7 # Copyright (C) 2010  Maximilian Hoegner <hp.maxi@hoegners.de>
   8 #
   9 # This program is free software: you can redistribute it and/or modify
  10 # it under the terms of the GNU General Public License as published by
  11 # the Free Software Foundation, either version 3 of the License, or
  12 # (at your option) any later version.
  13 #
  14 # This program is distributed in the hope that it will be useful,
  15 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 # GNU General Public License for more details.
  18 #
  19 # You should have received a copy of the GNU General Public License
  20 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  21 #
  22
  23 ### Part one - Functions for dealing with points on a sphere ###
  24
  25 ### Part two - A tolerant parser for position strings ###
  26 import re
  27
  28
  29 class Parser:
  30     """ A parser class using regular expressions. """
  31
  32     def __init__(self):
  33         self.patterns = {}
  34         self.raw_patterns = {}
  35         self.virtual = {}
  36
  37     def add(self, name, pattern, virtual=False):
  38         """ Adds a new named pattern (regular expression) that can reference previously added patterns by %(pattern_name)s.
  39         Virtual patterns can be used to make expressions more compact but don't show up in the parse tree. """
  40         self.raw_patterns[name] = "(?:" + pattern + ")"
  41         self.virtual[name] = virtual
  42
  43         try:
  44             self.patterns[name] = ("(?:" + pattern + ")") % self.patterns
  45         except KeyError as e:
  46             raise (Exception, "Unknown pattern name: %s" % str(e))
  47
  48     def parse(self, pattern_name, text):
  49         """ Parses 'text' with pattern 'pattern_name' and returns parse tree """
  50
  51         # build pattern with subgroups
  52         sub_dict = {}
  53         subpattern_names = []
  54         for s in re.finditer(r"%\(.*?\)s", self.raw_patterns[pattern_name]):
  55             subpattern_name = s.group()[2:-2]
  56             if not self.virtual[subpattern_name]:
  57                 sub_dict[subpattern_name] = "(" + self.patterns[
  58                     subpattern_name] + ")"
  59                 subpattern_names.append(subpattern_name)
  60             else:
  61                 sub_dict[subpattern_name] = self.patterns[subpattern_name]
  62
  63         pattern = "^" + (self.raw_patterns[pattern_name] % sub_dict) + "$"
  64
  65         # do matching
  66         m = re.match(pattern, text)
  67
  68         if m == None:
  69             return None
  70
  71         # build tree recursively by parsing subgroups
  72         tree = {"TEXT": text}
  73
  74         for i in range(len(subpattern_names)):
  75             text_part = m.group(i + 1)
  76             if not text_part == None:
  77                 subpattern = subpattern_names[i]
  78                 tree[subpattern] = self.parse(subpattern, text_part)
  79
  80         return tree
  81
  82
  83 position_parser = Parser()
  84 position_parser.add("direction_ns", r"[NSns]")
  85 position_parser.add("direction_ew", r"[EOWeow]")
  86 position_parser.add("decimal_separator", r"[\.,]", True)
  87 position_parser.add("sign", r"[+-]")
  88
  89 position_parser.add("nmea_style_degrees", r"[0-9]{2,}")
  90 position_parser.add("nmea_style_minutes",
  91                     r"[0-9]{2}(?:%(decimal_separator)s[0-9]*)?")
  92 position_parser.add(
  93     "nmea_style", r"%(sign)s?\s*%(nmea_style_degrees)s%(nmea_style_minutes)s")
  94
  95 position_parser.add(
  96     "number",
  97     r"[0-9]+(?:%(decimal_separator)s[0-9]*)?|%(decimal_separator)s[0-9]+")
  98
  99 position_parser.add("plain_degrees", r"(?:%(sign)s\s*)?%(number)s")
 100
 101 position_parser.add("degree_symbol", r"°", True)
 102 position_parser.add("minutes_symbol", r"'|′|`|´", True)
 103 position_parser.add("seconds_symbol",
 104                     r"%(minutes_symbol)s%(minutes_symbol)s|″|\"",
 105                     True)
 106 position_parser.add("degrees", r"%(number)s\s*%(degree_symbol)s")
 107 position_parser.add("minutes", r"%(number)s\s*%(minutes_symbol)s")
 108 position_parser.add("seconds", r"%(number)s\s*%(seconds_symbol)s")
 109 position_parser.add(
 110     "degree_coordinates",
 111     r"(?:%(sign)s\s*)?%(degrees)s(?:[+\s]*%(minutes)s)?(?:[+\s]*%(seconds)s)?|(?:%(sign)s\s*)%(minutes)s(?:[+\s]*%(seconds)s)?|(?:%(sign)s\s*)%(seconds)s"
 112 )
 113
 114 position_parser.add(
 115     "coordinates_ns",
 116     r"%(nmea_style)s|%(plain_degrees)s|%(degree_coordinates)s")
 117 position_parser.add(
 118     "coordinates_ew",
 119     r"%(nmea_style)s|%(plain_degrees)s|%(degree_coordinates)s")
 120
 121 position_parser.add(
 122     "position", (
 123         r"\s*%(direction_ns)s\s*%(coordinates_ns)s[,;\s]*%(direction_ew)s\s*%(coordinates_ew)s\s*|"
 124         r"\s*%(direction_ew)s\s*%(coordinates_ew)s[,;\s]*%(direction_ns)s\s*%(coordinates_ns)s\s*|"
 125         r"\s*%(coordinates_ns)s\s*%(direction_ns)s[,;\s]*%(coordinates_ew)s\s*%(direction_ew)s\s*|"
 126         r"\s*%(coordinates_ew)s\s*%(direction_ew)s[,;\s]*%(coordinates_ns)s\s*%(direction_ns)s\s*|"
 127         r"\s*%(coordinates_ns)s[,;\s]+%(coordinates_ew)s\s*"
 128     ))
 129
 130
 131 def get_number(b):
 132     """ Takes appropriate branch of parse tree and returns float. """
 133     s = b["TEXT"].replace(",", ".")
 134     return float(s)
 135
 136
 137 def get_coordinate(b):
 138     """ Takes appropriate branch of the parse tree and returns degrees as a float. """
 139
 140     r = 0.
 141
 142     if b.get("nmea_style"):
 143         if b["nmea_style"].get("nmea_style_degrees"):
 144             r += get_number(b["nmea_style"]["nmea_style_degrees"])
 145         if b["nmea_style"].get("nmea_style_minutes"):
 146             r += get_number(b["nmea_style"]["nmea_style_minutes"]) / 60.
 147         if b["nmea_style"].get(
 148                 "sign") and b["nmea_style"]["sign"]["TEXT"] == "-":
 149             r *= -1.
 150     elif b.get("plain_degrees"):
 151         r += get_number(b["plain_degrees"]["number"])
 152         if b["plain_degrees"].get(
 153                 "sign") and b["plain_degrees"]["sign"]["TEXT"] == "-":
 154             r *= -1.
 155     elif b.get("degree_coordinates"):
 156         if b["degree_coordinates"].get("degrees"):
 157             r += get_number(b["degree_coordinates"]["degrees"]["number"])
 158         if b["degree_coordinates"].get("minutes"):
 159             r += get_number(b["degree_coordinates"]["minutes"]["number"]) / 60.
 160         if b["degree_coordinates"].get("seconds"):
 161             r += get_number(
 162                 b["degree_coordinates"]["seconds"]["number"]) / 3600.
 163         if b["degree_coordinates"].get(
 164                 "sign") and b["degree_coordinates"]["sign"]["TEXT"] == "-":
 165             r *= -1.
 166
 167     return r
 168
 169
 170 def parse_position(s):
 171     """ Takes a (utf8-encoded) string describing a position and returns a tuple of floats for latitude and longitude in degrees.
 172     Tries to be as tolerant as possible with input. Returns None if parsing doesn't succeed. """
 173
 174     parse_tree = position_parser.parse("position", s)
 175     if parse_tree == None: return None
 176
 177     lat_sign = +1.
 178     if parse_tree.get(
 179             "direction_ns") and parse_tree["direction_ns"]["TEXT"] in ("S",
 180                                                                        "s"):
 181         lat_sign = -1.
 182
 183     lon_sign = +1.
 184     if parse_tree.get(
 185             "direction_ew") and parse_tree["direction_ew"]["TEXT"] in ("W",
 186                                                                        "w"):
 187         lon_sign = -1.
 188
 189     lat = lat_sign * get_coordinate(parse_tree["coordinates_ns"])
 190     lon = lon_sign * get_coordinate(parse_tree["coordinates_ew"])
 191
 192     return lat, lon