How hard can this be?

[Patrick Kirk]

  if x > 0:
    print "x is positive"

You would think anyone could enter that but I can't.  I get the following:

>>> import math
>>> if x > 0:
...  print "x is positive"
...
Traceback (innermost last):
  File "<stdin>", line 1, in ?
NameError: x
>>>

I've tried creating a .py file saying:
  if x > 0:
    print "x is positive"
and importing it but that doesn't work either.

>>> import a
Traceback (innermost last):
  File "<stdin>", line 1, in
  File "a.py", line 1
    if x > 0:
    ^
SyntaxError: invalid syntax



The worrying thing is that this is copied directly from the tutorial so I
may well be off to Álan gould's site shortly.  But is there something
obvious that I'm missing?

Thanks in advance.