Loop Question

[Dave Angel]

On 06/24/2013 08:20 AM, Lutz Horn wrote:
> Hi,
>
> Am 24.06.2013 14:12 schrieb christhecomic at gmail.com:
>> username=raw_input("Please enter your username: ")
>> password=raw_input("Please enter your password: ")
>> if username == "john doe" and password == "fopwpo":
>>      print "Login Successful"
>> else:
>>      print "Please try again"
>
> while not username or not password or username != "john doe" or password
> != "fopwpo":
>      print "Please try again"
>      username=raw_input("Please enter your username: ")
>      password=raw_input("Please enter your password: ")
>
> print "Login Successful"
>
>

That requires you to have four raw_input() calls instead of two.  And 
what purpose does adding the two new clauses to the while test serve? 
How is:

while not username or not password or username != "john doe" or password 
!= "fopwpo":

different from:

while username != "john doe" or password != "fopwpo":

(other than taking more time and space, and being harder to read) ?

-- 
DaveA