Python try-except名称错误

Question

I am making a clock type program in Python which has the option for formatting. I've got a function where the background colour is assigned by a variable, but I want to make the program user-friendly. When the variable for the bg colour is a string like "black", it returns this:

      File "C:\Python27\lib\lib-tk\turtle.py", line 1105, in _colorstr
        raise TurtleGraphicsError("bad color string: %s" % str(color))
    TurtleGraphicsError: bad color string: black

And so I added the try except code which is meant to catch the TurtleGraphicsError error. However, when I run the code, this happens:

    except (TurtleGraphicsError):
NameError: name 'TurtleGraphicsError' is not defined

I've tried with and without brackets. Any idea why this is happening?

Python 2.7.12, Windows 8.1 Used imports are:

from datetime import datetime
from calendar import day_name
from time import sleep
import turtle
import os

Answer 1

The error message says it correctly, the name TurtleGraphicsError is not defined in that scope. It is defined inside the turtle package (hence it tells you turtle.TurtleGraphicsError). You can either import it like:

from turtle import TurtleGraphicsError

or use it's actual name

import turtle
try:
    ...
except turtle.TurtleGraphicsError:
    print(...)