Re: basic python question about for loop

[Jason Stokes]

"jmDesktop" <[EMAIL PROTECTED]> wrote in message 
news:[EMAIL PROTECTED]

> So what is n and x in the first iteration?  Sorry.  I'm trying.

Remember how Python's range operator works.  range(n, x) constructs a list 
that consists of all elements starting with n and up to, but /not 
including/, x.  For example, range(3, 7) constructs the list [3, 4, 5, 6].

So what happens if you try to construct the list range(2, 2)?  In this case, 
Python will construct an empty list -- this is its interpretation of "up to, 
but not including n" for an argument like range(n, n).  This is precisely 
what is happening in the first iteration of the first enclosing for loop. 
Trace through the code; see that 2 is bound to n in the first iteration; see 
that the inner loop then tries to construct the list range(2, n), which is 
range(2, 2), which is an empty list.  And a "for x in []" statement will not 
execute even once.

As it happens, your loop is perfectly correct.  You are testing for divisors 
for a number excluding 1 and the number itself.  For the number 2, the 
number of possible divisors satisfying this condition is an empty set.  So 2 
is, quite correctly, adjudged to be prime. 


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Re: Explicit variable declaration

[Jason Stokes]

"Filip Gruszczynski" <[EMAIL PROTECTED]> wrote in message 
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>>  If you want to just declare that name exist, but doesn't want to
>>  declare the type, why don't you just do this:
>>
>>  def somefunc():
>> nonlocal = nonlocal
>> local = 0 # or None or [] or an initial value
>> #
>> return nonlocal * local
>
> Err.. I don't quite get. How it may help me? Could you explain?

Hi Filip,

In Python the standard patten for "declaring" variables is just to assign to 
them as they are needed.  If you want the effect of a declaration as you 
would do in C, you can just define the variable and initialize it to 0 or 
None.  (Or {} for a new dictionary, or [] for a new list.)

eg,

def collaterecs():
recordscount = 0
recordlist = []
...
   return recordlist



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