scanning for numerals / letters

[Kun]

I have the following if statement that checks if a form is empty:

     if form.has_key("date") and form["date"].value != "":
         date=form['date'].value

     else:
         print "ERROR: No date entered!"
         raise Exception

I would also like to add another if statement checking if 'date' has any 
letters (a-z) in it, and if so, would like to say that "you have to 
enter a date with numbers".  I am not sure how to alter my current if 
statement to do that check so any assistance would be appreciated.


On the flip side, I also have a field called 'purchases' where the user 
must enter non-numerals, thus i would also like to know how to scan to 
see if their entry has numerals and print 'please do not use numbers' if 
they did.

Thanks for your help.