I'm struggling to create the __ str __ function (aka pretty print) with polynomials, where dictionaries are used to contain the powers as keys and the elements as coefficients. I have done it with lists but I haven't mastered dictionaries yet. Is there anything to improve?
You can see in the second polynomial that if my last constant is not a constant, after arranging the keys with the reverse() function, the plus is always there, what can i do to prevent that? By the way I am trying to overload operators, after I've done this I'll try to do __ add__, __ mul__, __ sub__, and __ call__... though I would finish this one first :P
class Polynomial(object):
def __init__(self, coefficients):
self.coefficients = coefficients
def __str__(self):
polyd = self.coefficients
exponent = polyd.keys()
exponent.reverse()
polytostring = ' '
for i in exponent:
exponent = i
coefficient = polyd[i]
if i == 0:
polytostring += '%s' % coefficient
break
polytostring += '%sx^%s + ' % (coefficient, exponent)
return polytostring
dict1 = {0:1,1:-1}
p1 = Polynomial(dict1)
dict2 = {1:1,4:-6,5:-1, 3:2}
p2 = Polynomial(dict2)
print p1
print p2
for loop will end(break) when exponent value is equal to 0.code:
class Polynomial(object):
def __init__(self, coefficients):
self.coefficients = coefficients
def __str__(self):
polytostring = ' '
for exponent, coefficient in self.coefficients.iteritems():
if exponent == 0:
polytostring += '%s + ' % coefficient
else:
polytostring += '%sx^%s + ' % (coefficient, exponent)
polytostring = polytostring.strip(" + ")
return polytostring
dict1 = {0:1, 1:-1}
p1 = Polynomial(dict1)
dict2 = {1:1, 4:-6, 5:-1, 3:2}
p2 = Polynomial(dict2)
print "First:-", p1
print "Second:-", p2
Output:
$ python poly.py
First:- 1 + -1x^1
Second:- 1x^1 + 2x^3 + -6x^4 + -1x^5