If a recursion never reaches a base case, it goes on making recursive calls forever, and the program never terminates. This is known as infinite recursion, and it is generally not a good idea. Here is a minimal program with an infinite recursion:
def recurse(): recurse()
In most programming environments, a program with infinite recursion does not really run forever. Python reports an error message when the maximum recursion depth is reached:
File "<stdin>", line 2, in recurse File "<stdin>", line 2, in recurse File "<stdin>", line 2, in recurse . . . File "<stdin>", line 2, in recurse RuntimeError: Maximum recursion depth exceeded
This traceback is a little bigger than the one we saw in the previous chapter. When the error occurs, there are 1000
recurse frames on the stack!