4.N.13

Apropos of the Sugar 4th grade math activity that David and I are working on, I wrote an integer like class that prints nicely and that allow each digit to be addressed as if it were a list.

__iter__ goes through the digits - allowing gui code to build digit boxes easily.

e.g.:

>>> print maths_4_N_13.LongDivFormatted(15670,3)
      5,223
   --------  R=1
 3 | 15,670
>>> 

from types import  IntType, LongType

THOUSANDS_SEP = ','
DECIMAL_SEP = ''

class TeachingWholeNumber(object):
    """An integer whole number (>= 0) where each digit is addressable
    list style.  the 0th element of the 'digits' attribute
    is the ones place, the 1st element is the
    tens place and so on.
    """

    def __init__(self,n=0):
        """New object with default value of 0
        """
        if n == 0:
            self.digits=[0]
        else:
            n=int(n)
            self.digits=[]
            while n > 0:
                self.digits.append(n%10)
                n=n/10

    def __int__(self):
        """Returns the corresponding integer value
        """
        retValue = 0
        for i,v in enumerate(self.digits):
            retValue += (10**i)*v
        return retValue


    #
    # listy methods
    #
    def __len__(self):
        """Returns the length of the digits list
        """
        return len(self.digits)

    def __getitem__(self,i):
        if type(i) not in (IntType,LongType):
            return TypeError, "Index must be an integer type"
        else:
            return self.digits[i]

    def __setitem__(self,i,v):
        if type(i) not in (IntType,LongType):
            return TypeError, "Index must be an integer type"
        if type(v) != IntType or v > 9 or v < 0:
            return ValueError, "value, v, must be an integer between 0 and 9"
        if i < len(self):
            self.digits[i]=v
        elif v > 0:
            # appending 0 past the last non-zero is a null op
            while i> len(self):
                self.digits.append(0)
            self.digits.append(v)

    #
    # Expected methods for number-like type
    #
    def __lt__(self, other):
        return int(self) < int(other)
    
    def __le__(self, other):
        return int(self) <= int(other)
    
    def __eq__(self, other):
        return int(self) == int(other)

    def __ne__(self, other):
        return int(self) != int(other)

    def __gt__(self, other):
        return int(self) > int(other)

    def __ge__(self, other):
        return int(self) >= int(other)

    def __add__(self, other):
        return self.__class__(int(self)+int(other))
    
    def __sub__(self, other):
        return self.__class__(int(self)-int(other))
    
    def __mul__(self, other):
        return self.__class__(int(self)*int(other))
    
    def __floordiv__(self, other):
        return self.__class__(int(self)/int(other))
    
    def __mod__(self, other):
        return self.__class__(int(self)%int(other))
    
    def __divmod__(self, other):
        return tuple([self.__class__(x)
                      for x in divmod(int(self),int(other))])
    
    def __pow__(self, other):
        return 
    
    def __lshift__(self, other):
        return NotImplemented
    
    def __rshift__(self, other):
        return NotImplemented
    
    def __and__(self, other):
        return NotImplemented
    
    def __xor__(self, other):
        return NotImplemented
    
    def __or__(self, other):
        return NotImplemented
    
    def __div__(self, other):
        return self.__class__(int(self)/int(other))
    
    def __truediv__(self, other):
        return NotImplemented
    
    def __neg__(self):
        return NotImplemented
    
    def __pos__(self):
        return NotImplemented

    def __abs__(self):
        return abs(int(self))

    def __invert__(self):
        return NotImplemented
    
    def __complex__(self):
        return NotImplemented

    def __long__(self):
        return long(int(self))

    def __float__(self):
        return float(int(self))

    def __repr__(self):
        return str(int(self))

    def __str__(self):
        """pretty string
        """

        dgtList=[]
        for i,v in enumerate(self):
            if i>0 and (i-1)%3 == 2:
                dgtList.append(THOUSANDS_SEP)
            dgtList.append(str(v))
        dgtList.reverse()
        return ''.join(dgtList)

    def rshift(self,places=1):
        """right shift (in base 10) disgarding 'places' least significant digits
        
        Arguments:
        - `self`:
        - `places`:
        """
        # is this better implememted by overriding >> ?
        
        while places > 0:
            self.digits.pop(0)
            places -= 1

    def lshift(self,places=1):
        """left shift (in base 10) disgarding 'places' least significant digits.
        Arguments:
        - `self`:
        - `places`:
        """
        # is this better implememted by overriding << ?
        while places > 0:
            self.digits.insert(0,0)
            places -= 1

def randomTWN(low,high):
    """factory fcn to return a random TeachingWholeNumber,
    between low and high inclusive.
    """

    if high < 0 or low < 0:
        raise ValueError, "high and low must be > 0"
    
    i = random.randint(low,high)
    return TeachingWholeNumber(i)
    

class Division (object):
    """Division Container
    """

    def __init__ (self,dividend,divisor):
        """New one!
        """
        self.dividend = dividend
        self.divisor = divisor
        self.quotent, self.remainder = divmod(dividend,divisor)


class LongDivFormatted(Division):
    """Knows how to print itself
    """
    leftMargin = 1
    rightMargin = 2
    midMargin = 1
    vertbar='|'
    horizbar='-'

    def __init__ (self,dividend,divisor,useTWN=True):
        """New one!
        """
        if useTWN:
            dividend=TeachingWholeNumber(dividend)
            divisor=TeachingWholeNumber(divisor)
        Division.__init__(self,dividend,divisor)


    def __str__ (self):
        """ASCII representation.
        """
        mainWidth = (self.leftMargin+
                     len(str(self.divisor))+
                     (self.midMargin *2)+
                     len(self.vertbar)+
                     len(str(self.dividend)))
        
        remainderWidth = ((self.rightMargin) +
                          len(str(self.remainder))+
                          len('R='))

        totalWidth = mainWidth+remainderWidth

        retLines=[]
        retLines.append(('%'+str(mainWidth)+'s')%(self.quotent))
        retLines.append((' '*(self.leftMargin +
                              len(str(self.divisor))+
                              self.midMargin)) +
                        (self.horizbar*(len(self.vertbar)+
                                        self.midMargin+
                                        len(str(self.dividend)))) +
                        ('%'+str(remainderWidth)+'s')%('R='+str(self.remainder)))
        retLines.append((' ' * self.leftMargin) +
                        str(self.divisor) +
                        (' ' * self.midMargin) +
                        self.vertbar +
                        (' ' * self.midMargin) +
                        str(self.dividend))
        
        return '\n'.join(retLines)