## pascal's triangle in python

I mentioned Pascal’s Triangle in the previous post, and after typing in the Oz code decided to make a Pascal’s Triangle pretty printer in python.

```
from sys import argv
def pascal(n):
if n == 1:
return [ [1] ]
else:
result = pascal(n-1)
lastRow = result[-1]
result.append( [ (a+b) for a,b in zip([0]+lastRow, lastRow+[0]) ] )
return result
def pretty(tree):
if len(tree) == 0: return ''
line = ' ' * len(tree)
for cell in tree[0]:
line += ' %2i' % cell
return line + "\n" + pretty(tree[1:])
if __name__ == '__main__':
print pretty( pascal( int(argv[1]) ) )
```

Which, when run with can generate something like this:

biblio:~/Projects/bookclub ed$ python pascal.py 9 1 1 1 1 2 1 1 3 3 1 1 4 6 4 1 1 5 10 10 5 1 1 6 15 20 15 6 1 1 7 21 35 35 21 7 1 1 8 28 56 70 56 28 8 1

It’s been fun reading up on the uses for Pascal’s triangle, although I imagine this is old hat for people more familiar with math than I. Still I think getting through this tome will be time well spent in the long run.