[Tutor] converting unkown amount of input into strings

[Julieta Rangel]

I have a dumb question.  I'm trying to write a program which differentiates 
polynomials.  In this program, the user enters the degree of the polynomial, 
and then is asked for the coefficients of the polynomial.  How can I store 
these coefficients into a list or into a string so that I can use them later 
in the following line:

r = Poly (c=[])

This is what I have so far:
import string
class Poly:
    def __init__ ( self, v = 'x', c = [0]):
        """__init__():
        Initializes a polynomial
        Default variable is x
        Default polynomial is zero"""
        self.var = v
        self.coef = c
        self.deg = len(c)-1
    def __str__ (self):
        """__str__():
        Converts a polynomial into a string"""
        x = `self.coef[0]`
        for i in range (1, self.deg+1):
            x = x + " + " + `self.coef[i]` + self.var + "^" + `i`
        return x

def Derivative(p):
    """Input: an instance of a polynomial
    Output: a polynomial that is the derivative of the input polynomial
    Side Effects: None"""
    pv=p.var
    pc=[]
    if p.deg==0:
        return Poly (v=pv,c=[0])
    else:
        for i in range(0,p.deg):
            d=(i+1)*p.coef[i+1]
            pc.append(d)
        return Poly (v=pv,c=pc)

I want the input (the coefficients)from the following line to be stored on a 
string, or list so that I can use them later on (keep scrolling until you 
find the place where I want to insert the coefficients entered)
a = input ("Enter the degree of your polynomial  ")

i = 1
while i<=a+1:

    b=a
    while b>=0:

    	w = input("Enter coefficient of x^ %s." % (b) )
        b=b-1
        i = i + 1
r = Poly (c=[w]) #  This is where I want to insert the coefficients.

Once the person enters the coefficients, how can I
# insert them inside the brackets.  The way I have it right now the program 
only considers the last coefficient entered, but I want the program to 
calculate the derivative of the entire input

p = Poly (c = [-1,1,2])
q = Poly (v = 'y', c = [-1,0,2,0,4,3])
m = Derivative(p)
n = Derivative(q)
o = Derivative(r)
print "The derivative of %s is: \n %s" % (p,m)
print " "
print "The derivative of %s is: \n %s" % (q,n)
print " "
print "The derivative of %s is: \n %s" % (r,o)
print " "

Again, any help will be greatly appreciated.

Julieta

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