[Tutor] attaching the first element in a list to a string
Benoit Dupire
bdupire@seatech.fau.edu
Thu, 03 May 2001 00:44:25 -0400
Julieta Rangel wrote:
> This modification to the program works well in calculating the integral, but
> it does not print it out when running the program. When you inputed
> poly.s.integrate() followed by print poly.s (In Python Shell), the integral
> is printed. What command should we include in the program to make it print
> out automatically while running it. If I include these commands in the
> actual program, they don't work as they do in Python Shell.
s is a Poly object defined in the 'poly' module, and s has a method called
'integrate'.
so to access s.integrate() from the interpreter, i input
import poly # this executes all the code in poly.py, and
therefore creates 's'
poly.s.integrate()
I do not need the 'poly.' part if i want to refer the object from the module
it lives in.
read my previous message carefully. The answer to your question was in there...
>integrate is now a method of the class Poly
>so i can use it like this...
>
>s= Poly( c=[1 5 6]) # here, we use __init__
>print s # here we use __str__
>s.integrate() # guess what ?
I advise you to read the Python tutorial (especially the part dealing with
modules) and/or the book called 'Learning Python', so that you can progress more
rapidly in Python.
Benoit
>
>
> Thanks for your help.
>
> Julieta
>
> >From: Benoit Dupire <bdupire@seatech.fau.edu>
> >To: Julieta Rangel <julieta_rangel@hotmail.com>
> >CC: tutor@python.org
> >Subject: Re: [Tutor] attaching the first element in a list to a string
> >Date: Wed, 02 May 2001 21:33:02 -0400
> >
> >I modified your program in this way:
> >
> >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
> > self.length = len(c)
> > 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 integrate(self):
> > """Input: an instance of a polynommial
> > Output: a polynomial that is the integral of the input polynomial
> > Side Effects: None"""
> >
> > coef=[0]
> > self.deg= self.deg +1
> > for i in range(0,self.deg):
> > coef.append(self.coef[i]/float(i+1))
> > self.coef= coef
> >
> >
> >degree = input('Enter the degree of your polynomial')
> >coef=[]
> >for i in range (0,degree + 1):
> > coefficient = input('Enter the coefficient for x^ %i ? ' %i)
> > coef.append(coefficient)
> >
> >s= Poly (c = coef)
> >
> >
> >
> >
> >The result is now the good one:
> > >>> reload(poly)
> >Enter the degree of your polynomial3
> >Enter the coefficient for x^ 0 ? 2
> >Enter the coefficient for x^ 1 ? 5
> >Enter the coefficient for x^ 2 ? 6
> >Enter the coefficient for x^ 3 ? 1
> ><module 'poly' from 'C:\Python20\poly.py'>
> > >>> poly.s.integrate()
> > >>> print poly.s
> >0+2.0x^1+2.5x^2+2.0x^3+0.25x^4
> >
> >
> >What are the difference with your program?
> >
> >integrate is now a method of the class Poly
> >so i can use it like this...
> >
> >s= Poly( c=[1 5 6]) # here, we use __init__
> >print s # here we use __str__
> >s.integrate() # guess what ?
> >
> >So the first argument of integrate() is now 'self' (the polynome itself)
> >I first increment the degree (because that's the definition of the
> >integration
> >of a polynom)
> >The first coeff should normally be 'k', we need an initial condition to set
> >it,
> >so for now i put 0
> >next coeff = coeff (degree 0) / (0+1)
> >next coeff = coeff (degree 1)/ (1+1)
> >etc...
> >When i have the new list of coeff, i set it for the current polynom (
> >self.coef= coef)
> >
> >You can also add your derivation function as a method, and use it like
> >s.derivate()
> >
> >Benoit
> >
> >
> >
> >
> >
> >
> >
> >Julieta Rangel wrote:
> >
> > > I have this problem. I'm trying to write a program that calculates the
> > > integral of a polynomial. 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
> > > self.length = len(c)
> > > 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
> > >
> > > class Poly2:
> > > def __init__ (self, v='x' , c = [0]):
> > > """__init__():
> > > Initializes a polynomial
> > > Default variable is x
> > > Default polynomial is zero"""
> > > self.var = v
> > > self.pc = c
> > > self.deg =len(c)-1
> > > self.length = len(c)
> > > def __str__(self):
> > > """__str__():
> > > Converts a second polynomial into a string"""
> > > x = `self.pc[0]`
> > > for i in range (0, self.deg+1):
> > > x = x + "+" +`self.pc[i]`+ self.var + "^" +`i+2`
> > > return x
> > >
> > > def Integrate(p):
> > > """Input: an instance of a polynommial
> > > Output: a polynomial that is the integral of the input polynomial
> > > Side Effects: None"""
> > > pv=p.var
> > > pc=[]
> > > for i in range(0,p.deg):
> > > I=p.coef[i+1]/float(i+2)
> > > pc.append(I)
> > > return Poly2 (v=pv,c=pc)
> > >
> > > degree = input('Enter the degree of your polynomial')
> > > coef=[]
> > > for i in range (0,degree + 1):
> > > coefficient = input('Enter the coefficient for x^ %i ? ' %i)
> > > coef.append(coefficient)#attach the coefficient entered to the end
> >of
> > > the
> > > #list named coef.
> > >
> > > s= Poly (c = coef)
> > > t= Integrate(s)
> > > # This is some code to test new functions
> > >
> > > print "The integral of %s is: \n %s" % (s,t)
> > > print " "
> > >
> > > My problem is that when I run it I get this:
> > >
> > > >>>reload(poly1)
> > > Enter the degree of your polynomial3
> > > Enter the coefficient for x^ 0 ? 2
> > > Enter the coefficient for x^ 1 ? 5
> > > Enter the coefficient for x^ 2 ? 6
> > > Enter the coefficient for x^ 3 ? 1
> > > The integral of 2+5x^1+6x^2+1x^3 is:
> > > 2.5+2.5x^2+2.0x^3+0.25x^4
> > >
> > > As you can see, the answer would be right if it weren't for the first
> >term
> > > in the polynomial. The first term should be a 2x, so the answer should
> >look
> > > like this: 2x^1+2.5x^2+2x^3+0.25x^4. Can anyone help me fix this
> >problem?
> > > I think that I need to find a way to have the first term on the list
> >labeled
> > > pc, which is 2 to be taken into consideration on the string representing
> >the
> > > polynomial. Am I right? If so, How can I accomplish this? Also, I
> >need to
> > > find a way so that when the coefficient of x^0 ==0 , the output should
> > > display a constant c along with the result, so that the answer looks
> >like
> > > c+2.5x^2+2x^3+0.23x^4.
> > > Can anyone guide me in the right direction? All inputs or comments
> >about my
> > > program are welcomed and appreciated.
> > >
> > > Julieta
> > >
> > > _________________________________________________________________
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> > >
> > > _______________________________________________
> > > Tutor maillist - Tutor@python.org
> > > http://mail.python.org/mailman/listinfo/tutor
> >
> >--
> >Benoit Dupire
> >Graduate Student
> >----------------
> >I'd like to buy a new Boomerang. How can i get rid of the old one?
> >
> >
>
> _________________________________________________________________
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>
> _______________________________________________
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--
Benoit Dupire
Graduate Student
----------------
I'd like to buy a new Boomerang. How can i get rid of the old one?