Gaussian Elimination: Python

def gausselim(a,b):
    '''gausselim a on the left, b on the right.'''
    for i in range(len(a)):
        a[i].append(b[i]*1.0)
        for j in range(len(a)):
            a[i][j] = a[i][j]*1.0 #Insert b to a and make sure these fucking numbers are float
    for k in range(len(a)-1):
        for i in range(k+1,len(a)):
            r = a[i][k]/a[k][k]
            for j in range(k,len(a)+1):
                if a[i][j]:
                    a[i][j] = a[i][j] - a[k][j]*r
    #Solving phase
    x = [0]*len(a)
    for i in range(len(a)-1,-1,-1):
        for j in range(i,len(a)-1):
            a[i][len(a)] = a[i][len(a)] - a[i][j+1]*x[j+1]
        x[i] = a[i][len(a)]/a[i][i]
    return x