On Thu, 25 Apr 2013 08:01:09 -0700, eternaltheft wrote:
> Hi guys, I'm having a lot of trouble with this.
>
> My understanding of python is very basic and I was wondering how I can
> return this table as a list of lists.
>
> 1 2 3 4 5
> 3 4 5 6
> 5 6 7
> 7 8
> 9
Do you know how to build lists of numbers?
a = [1, 2, 3, 4, 5]
b = [3, 4, 5, 6]
c = [5, 6, 7]
d = [7, 8]
e = [9]
Now put them in a list:
table = [a, b, c, d, e]
print table
Got that so far? Now let's see how you might do the same thing without
typing up the inner lists by hand. For that, you want the range()
function.
a = range(1, 6) # 1 is included, 6 is excluded.
b = range(3, 7)
c = range(5, 8)
# etc.
Now let's do it without the temporary variables a, b, c, d, e.
This time, start with the outer list, only with nothing in it. Then fill
it using the range function.
table = []
table.append(range(1, 6))
table.append(range(3, 7))
# etc.
Now let's put this in a function:
def table(n):
# Returns a triangular table (list of lists).
# So far, we ignore n and hard-code the table. We'll fix this later.
table = []
table.append(range(1, 6))
table.append(range(3, 7))
# etc.
return table
You're about halfway there now. The easy half. You get to do the hard
half :-)
You need to think about how to turn a series of repeated appends into a
loop, either a while loop or a for loop. I recommend you use a for-loop.
Start by answering these questions:
* if the argument to the function, n, is 4, how many rows and how many
columns will the table have?
* if n is 5, how many rows and columns will the table have?
* in general, for some value of n, what will be the first row?
* turn that into a call to range. Remember that if you call range with
two arguments, the first argument is included, the second is excluded:
range(5, 9) => [5, 6, 7, 8]
* what will the second row be? Hint: the *first* number in the second row
will be the first number of the first row PLUS TWO; the *last* number in
the second row will be ... what?
* turn that into a call to range. Can you see the pattern for how each
call to range will vary from the last?
* this suggests you want a for loop:
for row number 1, 2, 3, ...
table.append(make a row)
Obviously that's not real Python code. You need to write the Python code.
Write some code, and if you run into trouble, come back and ask for help.
Good luck!
--
Steven
--
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