On 26 March 2013 23:59, <rahulredd...@hotmail.com> wrote:
> So i have a set of for loops that create this :
>
> ***************************************
> *** *** *** *** *** *** ***
> *** *** *** *** *** *** ***
> *** *** *** *** *** *** ***
> *** *** *** *** *** *** ***
> ***************************************
>
> *
> ***
> *****
> *******
> *********
>
> but i want to nest all the loops under one BIG loop that'll run in reverse to
> make this:
>
> ***************************************
> *** *** *** *** *** *** ***
> *** *** *** *** *** *** ***
> *** *** *** *** *** *** ***
> *** *** *** *** *** *** ***
> ***************************************
>
> *
> ***
> *****
> *******
> *********
> *******
> *****
> ***
> *
> ***************************************
> *** *** *** *** *** *** ***
> *** *** *** *** *** *** ***
> *** *** *** *** *** *** ***
> *** *** *** *** *** *** ***
> ***************************************
>
> Is this possible?
Let's have a look at a simple example. Imagine you have a function:
>>> def print_pretty_pattern():
... for i in range(1, 6):
... print '*'*i
...
>>> print_pretty_pattern()
*
**
***
****
*****
You can't reverse the pattern because it's not data so you need to
turn it into data:
>>> def generate_pretty_pattern():
... for i in range(1, 6):
... yield '*'*i
It's the same as above, but the 'print' statement has been replace
with a 'yield' statement, making the function into a generator
function, so that when you call it you get an iterable of all the
lines. You can now make a function to print a pattern:
>>> def print_pattern(lines):
... for line in lines:
... print line
Or if you want to be concise:
>>> def print_pattern(lines):
... print "\n".join(lines)
So you can print any pattern:
>>> print_pattern(generate_pretty_pattern())
*
**
***
****
*****
So now you can write another generator that makes the mirror pattern
of a given pattern:
>>> def mirror_pattern(pattern):
... lines = []
... for line in pattern:
... yield line
... lines.append(line)
... if lines:
... lines.pop() # don't repeat the last line
... for line in reversed(lines):
... yield line
...
>>> print_pattern(mirror_pattern(generate_pretty_pattern()))
*
**
***
****
*****
****
***
**
*
Here's another example:
>>> print_pattern(mirror_pattern(''.join(mirror_pattern("*".ljust(i).rjust(15)))
>>> for i in range(1,16,2)))
*
* *
* *
* *
* *
* *
* *
* *
* *
* *
* *
* *
* *
* *
*
--
Arnaud
--
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