Add python3 backend.

Author: dvc94ch

Makefile

@@ -12,7 +12,7 @@ clean-java:
 	rm -f java/*
 
 python3: $(GRAMMAR) $(GRAMMAR_FILES)
-	$(ANTLR) -Dlanguage=Python3 $< -o python3/
+	$(ANTLR) -Dlanguage=Python3 $< -o python3/antlr
 
 clean-python3:
 	rm -f python3/*

python3/.gitignore

@@ -0,0 +1,7 @@
+__pycache__/
+dist/
+MANIFEST
+.cache/
+*.pyc
+Pipfile.lock
+antlr/ElectroGrammar*

python3/Pipfile

@@ -0,0 +1,19 @@
+[[source]]
+
+url = "https://pypi.python.org/simple"
+verify_ssl = true
+name = "pypi"
+
+
+[packages]
+
+"antlr4-python3-runtime" = "*"
+
+
+[dev-packages]
+
+
+
+[requires]
+
+python_version = "3.6"

python3/antlr/__init__.py

@@ -0,0 +1,37 @@
+from antlr4 import *
+from antlr.ElectroGrammarLexer import ElectroGrammarLexer
+from antlr.ElectroGrammarListener import ElectroGrammarListener
+from antlr.ElectroGrammarParser import ElectroGrammarParser
+
+
+class ElectroGrammarToObjectListener(ElectroGrammarListener):
+    def __init__(self):
+        self.obj = {}
+
+    def enterCapacitance(self, ctx):
+        cprefix_lookup = {'u': 10e-6, 'n': 10e-9, 'p': 10e-12}
+        number = float(str(ctx.NUMBER()))
+        cprefix = str(ctx.CPREFIX())
+        self.obj['capacitance'] = number * cprefix
+
+
+def parse(input):
+    lexer = ElectroGrammarLexer(input)
+    stream = CommonTokenStream(lexer)
+    parser = ElectroGrammarParser(stream)
+    tree = parser.electro_grammar()
+    listener = ElectroGrammarToObjectListener()
+    walker = ParseTreeWalker()
+    walker.walk(listener, tree)
+    return listener.obj
+
+
+def main(argv):
+    input = InputStream(argv[1])
+    tree = parse(input)
+    print(tree)
+
+
+if __name__ == '__main__':
+    import sys
+    main(sys.argv)

python3/electro_grammar.py

@@ -5,6 +5,8 @@
 grammar ElectroGrammar;
 import Alphabet;
 
+electro_grammar : capacitance;
+
 capacitance : NUMBER CPREFIX FARAD?;
 
 fragment DIGIT: [0-9];