grasshopper python Runtime error

Hi guys,

i am learning python for grasshopper recently, but there are some odd problems that i can't figure out. today i typed some code in python following a video tutorial step by step, but it did't work when i finished, saying as follows:

Runtime error (MissingMemberException): walker instance has no attribute 'x'
Traceback:
line 21, in step, "<string>"
line 34, in script

the code is as follows:

import rhinoscriptsyntax as rs
import random as r

r.seed(seed)

#class
class walker:
def _init_(self):
self.x = 0
self.y = 0

def point(self):
shape = rs.AddPoint(self.x, self.y, 0)
return shape

def step(self):
choice = r.randint(0,3)
if choice == 0:
self.x = self.x + 1
elif choice == 1:
self.x = self.x - 1
elif choice == 2:
self.y = self.y + 1
else:
self.y = self.y - 1

#time
w = walker()

pList = []
for t in range(time):
w.step()

pList.append(w.point())

a = pList

can anyone help me figure it out?

thanks

file attached

grasshopper version 0.9.0064

Attachments:

GH python.gh, 6 KB

Replies to This Discussion

Permalink Reply by djordje on January 29, 2014 at 4:03am

Hi Chunwei,

You made a typo: python constructor has two underscores in front and after "init": __init__
You typed one. What happens is that when you perform an instantiation of your "w" object, it does not automatically run the __init__ method, as it hasn't been written correctly. Therefor the self.x and self.y inside of it, do not get their values (0) assigned. So when you try to execute your solution, and it gets up the the line: self.x = self.x + 1, it does not know which value it needs to assign to self.x.

By the way this is not really a frequent questions.
Try moving this topic of yours from "FAQ (Frequent Questions and Problems)" section to "VB, C# and Python Coding". See here how to do that:

For all future questions on coding, post your topic it that section.
Thanks.

Permalink Reply by Chunwei Zhang on January 29, 2014 at 5:15am

Hi djordje,

thanks for your so detailed explaination:) i will move my question to the right section.

thanks again.

Permalink Reply by Igor Mitrić Lavovski on February 16, 2015 at 12:14pm

Thanks for this! same typo :)

Permalink Reply by Roig on March 15, 2017 at 6:40pm

thanks a lot, even 3 years later for me ;)

Just to take little step forward I tried to draw a polyline with the points in the list "a":

a = plist
path = rs.AddPolyline(a)

runs ok but trying to use the points from "a" as spheres centers with this:

sph = rs.AddSphere(a,rd)

its says: Could not convert [<System.Guid object at 0x0000000000000C0C [878bf11a-629b-46c4-ac7c-ac0dfcdda377]>] to a Point3d (it can't convert a list [] to a point3D)

do i need to feed addsphere with single points one at a time? can't I use a list?

I know it must be one of the simplest questions ever but would be grateful for any advice¡¡

Permalink Reply by Giulio Piacentino on January 29, 2014 at 4:49am