[IPython-user] difficulty with editing a multiline input

[Good Bad]

I find it difficult to edit a multiline input

I define the following function in IPython:

In [2]: def gen(n):
   ...:     while n:
   ...:         n = n - 1
   ...:         yield n

the cursor (the text cursor) is still in the last line of In [2].
how can i move the cursor up? for instance when I want to change n - 1 to n - 2? What if I want to insert another line like the following?

In [2]: def gen(n):
   ...:     while n:
   ...:         print n
   ...:         n = n - 1
   ...:         yield n