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lf in reply to @wence
were you saying my function was very C-like?

i've actually just re-written it and it's almost bang on the same as yours with enumerate - had seen a few people talking about that so tried to get that working. still not entirely sure what the :: does in grid[::d], apart from take every d'th y.

my function:
```
def findTrees2(funcdata, dx, dy):
    numTrees = 0
    for i, line in enumerate(funcdata[::dy]):
        if line[(i*dx) % len(line)] == '#': numTrees += 1
    return numTrees
```
edit: was also confused as to why you can't print an enumerate object until you put it into a list. but guess that's a conversation for data structures... i should really do a bit more formal learning

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useless in reply to @lf
still not entirely sure what the :: does in grid[::d], apart from take every d'th y

The slice syntax is
```
grid[start:stop:stride]
```
and you can omit any, so start defaults to zero, stop to -1 (which means the end, since negative indices count backwards), and stride defaults to 1.
- grid[start] just gives you the element at index start (ie, the half-open interval [start,start+1) in maths language),
- [start:stop] gives you the sub-sequence/sub-string with default stride 1,
- [start::stride] would give you every stride'th element from start to the end, etc.

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lf in reply to @useless

Thanks - i had never seen the stride part of the syntax, always just sliced [x:y]
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Tijmen in reply to @useless

This is great, just doing the challenges is already good for my programming skills but info like this and things previously posted by @Greenbank are even better. Helps me move away from hacky solutions to proper solutions.

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