vim python 龟窗口

Question

I'm on a Mac with macOS Mojave v. 10.14.3 . I'm using vim per professors edict. I learning python as part of a unix class. My first lines in vim are:

import turtle             # Allows us to use turtles
wn = turtle.Screen()      # Creates a playground for turtles
alex = turtle.Turtle()    # Create a turtle, assign to alex

alex.forward(50)          # Tell alex to move forward by 50 units
alex.left(90)             # Tell alex to turn by 90 degrees
alex.forward(30)          # Complete the second side of a rectangle

wn.mainloop()             # Wait for user to close window

These lines are copied from: How to Think Like a Computer Scientist: Learning with Python 3

Doing w | !python % on the command line yields:

the window appears and immediately vanishes!

with:

Traceback (most recent call last):
  File "turtle", line 2, in <module>
    wn = turtle.Screen()      # Creates a playground for turtles
  File "/usr/lib/python2.7/lib-tk/turtle.py", line 3553, in Screen
    Turtle._screen = _Screen()
  File "/usr/lib/python2.7/lib-tk/turtle.py", line 3569, in __init__
    _Screen._root = self._root = _Root()
  File "/usr/lib/python2.7/lib-tk/turtle.py", line 458, in __init__
    TK.Tk.__init__(self)
  File "/usr/lib/python2.7/lib-tk/Tkinter.py", line 1823, in __init__
    self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.TclError: no display name and no $DISPLAY environment variable

I tried the same thing using ssh to my RPi (what we use for learning about the kernel) and got:

the window appears and immediately disappears; as above. I didn't copy the shell response; I wanted to try the following.

I then tried logging directly into the RPi with full 'windows' regalia after shutdown and tried the same script and the same command line entry and got:

The same window problem with the addition of what appeared to be drawing on the window before disappearing. Further:

Traceback (most recent call):
   File "turtle", line 9, in <module>
     wn.mainloop()        # wait for user to close window
AttributeError: '_screen' object has no attribute 'mainloop'

I hope I'm not too through.
I'll not see the professor for another 2 weeks and possibly longer as I'm to have shoulder surgery.

Answer 1

Even today, Apple's Mac OS X by default supplies multiple versions of Python 2 (invoked as python at the command line) and no versions of Python 3. You should install your own Python 3 (typically invoked as python3 at the command line.)

You can also make code this basic insensitive to the difference:

import turtle  # Allows us to use turtles

wn = turtle.Screen()  # Creates a playground for turtles
alex = turtle.Turtle()  # Create a turtle, assign to alex

alex.forward(50)  # Tell alex to move forward by 50 units
alex.left(90)  # Tell alex to turn by 90 degrees
alex.forward(30)  # Complete the second side of a rectangle

wn.exitonclick()  # Wait for user to close (or click on) window

The above should run the same on either major version of Python.