python turtle graphic doesn't draw

Question

When I run the following code it only pops up a window and doesn't draw any graphic.

I tried a few examples from references but in all cases, it happened. Can someone help me to fix the problem?

import turtle
turtle.mainloop()
t = turtle.Turtle()
t.color('red')
t.pensize(10)
t.shape('turtle')

Answer 1

See here:

https://docs.python.org/3.1/library/turtle.html#turtle.mainloop

Starts event loop - calling Tkinter's mainloop function. Must be the last statement in a turtle graphics program. Must not be used if a script is run from within IDLE in -n mode (No subprocess) - for interactive use of turtle graphics.

So you have the second line to the end of your program

Also without mainloop i can see an red Turtle drawn when run in repl.it: https://repl.it/@CarstenEggers/Raphael

Answer 2

The reason it's not doing anything is because you haven't actually told the "draw-er" t to draw anything. All the stuff you've told it to do is just set-up instructions: what color to use, what size to draw at, etc.

Try running this code instead. Explanations in comments:

import turtle
# turtle.mainloop()  # Generally not necessary to run mainloop; can just delete
t = turtle.Turtle()  # Creating a turtle to do drawing
t.color('red')  # Telling it what color to draw
t.pensize(10)  # Telling it what size to draw at
t.shape('turtle')  # What shape turtle draw-er should be: "arrow", "turtle", etc

# Now let's draw something!
t.forward(50)  # Tell turtle to draw in forward direction 50 pixels
t.left(80)  # Tell turtle to turn in-place 80 degrees to left
t.forward(100)  # Draw 100 pixels forward
t.right(90)  # Turn in-place 90 degrees right
t.forward(170)  # Draw 170 pixels forward
# Done drawing!

turtle.exitonclick()  # Tell program to keep picture on screen, exit on click
# Note: See how that's `turtle` and not `t`? That's because we don't want to
# tell our draw-er `t` anything: `t` is just for drawing, it doesn't control
# the larger scope of starting and exiting. If we said `t.exitonclick()`, the
# program would just break at the end, because the draw-er does not know how
# to exit or anything.
# On the the other hand, the module `turtle` (where we get the draw-er and
# everything else from) does know how to handle starting and exiting, so that's
# why we make the call to the module itself instead of the draw-er `t`.