In Section 3.10, we used a stack diagram to represent the state of a program during a function call. The same kind of diagram can help interpret a recursive function.
Every time a function gets called, Python creates a new function frame, which contains the function’s local variables and parameters. For a recursive function, there might be more than one frame on the stack at the same time.
Figure 5.9.1 shows a stack diagram for
countdown called with
n = 3.
As usual, the top of the stack is the frame for
__main__. It is empty because we did not create any variables in
__main__ or pass any arguments to it.
countdown frames have different values for the parameter
n. The bottom of the stack, where
n=0, is called the base case. It does not make a recursive call, so there are no more frames.
Draw a stack diagram for
print_n called with
s = 'Hello' and
Write a function called
do_n that takes a function object and a number, n, as arguments, and that calls the given function