CODEWITHSUNDEEP
pythonlist
diegoaguilar
diegoaguilar

Reputation: 8376

Iterating over a two lists of integers in python?

I'm coding a function to produce Lagrange Interpolation, being enter image description here expression.

Given two lists: Xs and Ys and so x I wrote the algorithm below:

#!/usr/bin/env python
#coding: utf8 
from sympy import *
from numpy import *
import json

L = {}
x = Symbol('x')
expresion = ''
def lagrange(Xs, Ys, x):

    for k in len(Xs):

        if k != 0 or k != len(Xs)-1: #si no es el primero o el último término de la sumatoria
            expresion = expresion + '+' + Ys[k] + '*'
        elif k==0:
            expresion = expresion + Ys[k] + '*'
        for i in len(Xs):
            if k==i:
                continue # Si i==k saltamos esta iteración para eliminar división sobre cero
            expresion = expresion + '(' + '(' + x + '-' + Xs[i] +' )' + '/' + '(' + Xs[k] + '-' + Xs[i] + ')' +')'
    print simpify(expresion)

When I ran:

#!/usr/bin/env python
#coding: utf8 

from lagrange import *

lagrange([0,1,2,4],[-1,0,7,4,63],3)

I got:

[......]line 12, in lagrange
    for k in len(Xs):
TypeError: 'int' object is not iterable
[Finished in 0.5s with exit code 1]

So how should I iterate over Xs and Ys elements and so include condition that if i=k it will continue over the loop?

Upvotes: 0

Views: 81

Answers (1)

C.B.
C.B.

Reputation: 8326

for k in range(len(Xs))

Will give you all the possible indicies in Xs.

len(Xs) simply returns an int, which is not iterable. You would want to do the same for your i loop.

Upvotes: 2

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