logo.py

class Operation:
    def __eq__(self, other):
        return self.__class__ == other.__class__

    def matches(self, line):
        def zip_strs(a, b):
            def separate(str):
                return [char for char in str]
            return zip(separate(a), separate(b))
        self.match_args = []
        
        for syntax_part, line_part in zip_strs(self.syntax, line):
            if syntax_part == '%':
                arg = line_part
                self.match_args.append(arg)
            elif syntax_part != line_part:
                return False
        
        return True

    def match(self):
        return self.__class__(*self.match_args)

class Pen(Operation):
    syntax = 'P %'

    def __init__(self, number=0):
        self.number = int(number)

    def __eq__(self, other):
        return self.number == other.number

class Down(Operation): syntax = 'D'
class Up(Operation): syntax = 'U'

class Direction(Operation):
    def __init__(self, amount=0):
        self.amount = int(amount)
    
    def __eq__(self, other):
        return self.amount == other.amount

class East(Direction): syntax = 'E %'
class North(Direction): syntax = 'N %'
class South(Direction): syntax = 'S %'
class West(Direction): syntax = 'W %'

class Parser:
    def __init__(self, operations):
        self.operations = operations
    
    def parse(self, line):
        ret = []
        for line in code.splitlines():
            ret.append(self.parse_line(line))

        return ret

    def parse_line(self, line):
        for operation in self.operations:
            if operation.matches(line):
                return operation.match()

code = '''P 2  # select pen 2
D    # pen down
W 2  # draw west 2cm
N 1  # then north 1
E 2  # then east 2
S 1  # then back south
U    # pen up'''

operations = (Pen(), Down(), West(), North(), East(), South(), Up(), )
parser = Parser(operations)
result = parser.parse(code)

assert result[0] == Pen(2)
assert result[1] == Down()
assert result[2] == West(2)
assert result[3] == North(1)
assert result[4] == East(2)
assert result[5] == South(1)
assert result[6] == Up()