'range' object does not support item assignment in python3

Question

How to solve this error:

File "rainbow.py", line 53, in plot_rainbow

xr[0],yr[0] = offset_curve(ax, x,y, lw/2.)

TypeError: 'range' object does not support item assignment

in the following code, please? I tried to replace range with xrange, but it does not help.

import numpy as np
import matplotlib.pyplot as plt
dpi = 100
def offset(x,y, o):
 """ Offset coordinates given by array x,y by o """
 X = np.c_[x,y].T
 m = np.array([[0,-1],[1,0]])
 R = np.zeros_like(X)
 S = X[:,2:]-X[:,:-2]
 R[:,1:-1] = np.dot(m, S)
 R[:,0] = np.dot(m, X[:,1]-X[:,0])
 R[:,-1] = np.dot(m, X[:,-1]-X[:,-2])
 On = R/np.sqrt(R[0,:]**2+R[1,:]**2)*o
 Out = On+X
 return Out[0,:], Out[1,:]
def offset_curve(ax, x,y, o):
 """ Offset array x,y in data coordinates
 by o in points """
 trans = ax.transData.transform
 inv = ax.transData.inverted().transform
 X = np.c_[x,y]
 Xt = trans(X)
 xto, yto = offset(Xt[:,0],Xt[:,1],o*dpi/72. )
 Xto = np.c_[xto, yto]
 Xo = inv(Xto)
 return Xo[:,0], Xo[:,1]
# some single points
y = np.array([1,2,2,3,3,0]) 
x = np.arange(len(y))
#or try a sinus
x = np.linspace(0,9)
y=np.sin(x)*x/3.
fig, ax=plt.subplots(figsize=(4,2.5), dpi=dpi)
cols = ["#fff40b", "#00e103", "#ff9921", "#3a00ef", "#ff2121", "#af00e7"]
lw = 2.
lines = []
for i in range(len(cols)):
 l, = plt.plot(x,y, lw=lw, color=cols[i])
 lines.append(l)
def plot_rainbow(event=None):
 xr = range(6); yr = range(6); 
 xr[0],yr[0] = offset_curve(ax, x,y, lw/2.)
 xr[1],yr[1] = offset_curve(ax, x,y, -lw/2.)
 xr[2],yr[2] = offset_curve(ax, xr[0],yr[0], lw)
 xr[3],yr[3] = offset_curve(ax, xr[1],yr[1], -lw)
 xr[4],yr[4] = offset_curve(ax, xr[2],yr[2], lw)
 xr[5],yr[5] = offset_curve(ax, xr[3],yr[3], -lw)
 for i in range(6): 
 lines[i].set_data(xr[i], yr[i])
plot_rainbow()
fig.canvas.mpl_connect("resize_event", plot_rainbow)
fig.canvas.mpl_connect("button_release_event", plot_rainbow)
plt.savefig(__file__+".png", dpi=dpi)
plt.show()

I try to compile the code from this question.

Answer 1

range object can not be set.

You can change it to list by:

 xr = list(range(6)); yr = list(range(6)); 

But I don't understand why you use in range in the first place. If you just wan to initialize a list, I would go with something like:

xr, yr = 6*[None], 6*[None]

Ofcourse you can put 0 or whatever instead None

Answer 2

range() returns range object instead of list. To convert:

xr = list(range(6))