[Tutor] skipping ahead within a loop

[Kent Johnson]

Rikard Bosnjakovic wrote:
> On 3/15/07, Clay Wiedemann <clay.wiedemann at gmail.com> wrote:
>> If  doing a loop, how can one skip forward a specific amount randomly
>> determined within the loop?
> 
> y = 0
> while y < HEIGHT:
>   linewidth = random(3, 9)
>   # drawlines etc
>   y += linewidth
> 
> The reason why you cannot alter the for-variable beats me, though.

Because each time through the loop the variable is assigned to the next 
value from the range.

A Python for loop is not like a C for loop. Python for loops work with 
sequences. The loop variable is assigned to each element of the sequence 
in turn.

range() returns a list which is the sequence the for loop iterates over.

You can manipulate the loop by making the iterator explicit. For example:
 >>> for i in it:
...     print i
...     it.next() # explicitly skip the next item
...
0
2
4
6

Kent