ocr.py

class OCR :
	
	contains_set = {
		(0, 1) : set([0, 2, 3, 5, 6, 7, 8, 9]),
		(1, 0) : set([0, 4, 5, 6, 8, 9]),
		(1, 1) : set([2, 3, 4, 5, 6, 8, 9]),
		(1, 2) : set([0, 1, 2, 3, 4, 7, 8, 9]),
		(2, 0) : set([0, 2, 6, 8]),
		(2, 1) : set([0, 2, 3, 5, 6, 8, 9]),
		(2, 2) : set([0, 1, 3, 4, 5, 6, 7, 8, 9])
	}
	
	def parse_number(self, number):
		full_list = set(range(10))
		dont_contains_set = {}
		for i in range(3):
			for j in range(3):
				try:
					the_set = self.contains_set[i, j]
					dont_contains_set[i, j] = full_list.difference(the_set)
					if number[i][j] == ' ':
						full_list = full_list.intersection(dont_contains_set[i, j])
					else:
						full_list = full_list.intersection(self.contains_set[i, j])
				except KeyError:
					pass
				
				if len(full_list) == 1:
					return list(full_list)[0]
	
	def parse_account(self, input_str):
		if len(input_str.splitlines()) != 4:
			raise WrongInputError
		
		lines = input_str.splitlines()[1:]
		for line in lines:			
			if len(line) != 27:
				raise WrongInputError("Wrong columns size: %d." % len(line))
				
			l = line.replace(' ', '').replace('_', '').replace('|', '')
			if len(l) > 0:
				raise WrongInputError("Invalid character found!")
		
		to_return = ''
		for i in range(0, 27, 3):
			mat = []
			mat.append(lines[0][i:i+3])
			mat.append(lines[1][i:i+3])
			mat.append(lines[2][i:i+3])
			
			to_return += str(self.parse_number(mat))
			
		return int(to_return)

class WrongInputError(Exception):
	pass

test_ocr.py

import unittest
from nose.tools import *
from ocr import *

class OCRSpec(unittest.TestCase):
	
	def setUp(self):
		self.ocr = OCR()
	
	@raises(WrongInputError)
	def it_should_raise_exception_when_input_is_wrong(self):
		input_str = \
		"""
$    _  _  _  _  _  _     _ 
$|_||_|| || ||_   |  |  ||_ 
$  | _||_||_||_|  |  |  | _|"""
		self.ocr.parse_account(input_str)

	@raises(WrongInputError)
	def it_should_only_accept_pipe_spaces_and_underline(self):
		input_str = \
"""
    _  _  _  _  _  _     _ 
|_||2|| || ||_   |  |  ||_ 
  | _||_||_||_|  |  |  | _|"""
		self.ocr.parse_account(input_str)
		
	def it_should_return_490067715(self):
		input_str = \
"""
    _  _  _  _  _  _     _ 
|_||_|| || ||_   |  |  ||_ 
  | _||_||_||_|  |  |  | _|"""
		assert_equals(self.ocr.parse_account(input_str), 490067715)
		
	def it_should_return_490067716(self):
		input_str = \
"""
    _  _  _  _  _  _     _ 
|_||_|| || ||_   |  |  ||_ 
  | _||_||_||_|  |  |  ||_|"""
		assert_equals(self.ocr.parse_account(input_str), 490067716)
		
		
	def it_should_return_123456789(self):
		input_str = \
"""
    _  _     _  _  _  _  _ 
  | _| _||_||_ |_   ||_||_|
  ||_  _|  | _||_|  ||_| _|"""
		assert_equals(self.ocr.parse_account(input_str), 123456789)
		
	def it_should_have_3_lines_and_27_colums_per_line(self):
		input_str = \
"""
    _  _  _  _  _  _     _ 
|_||_|| || ||_   |  |  ||_ 
  | _||_||_||_|  |  |  | _|"""
		self.ocr.parse_account(input_str)
		
	def it_should_return_8(self):
		input_matrix = [' _ ', '|_|', '|_|']
		assert_equals(self.ocr.parse_number(input_matrix), 8)
		
	def it_should_return_4(self):
		input_matrix = ['   ', '|_|', '  |']
		assert_equals(self.ocr.parse_number(input_matrix), 4)
		
	def it_should_return_1(self):
		input_matrix = ['   ', '  |', '  |']
		assert_equals(self.ocr.parse_number(input_matrix), 1)