[Tutor] how to sort the data inside the file.

[Kent Johnson]

Chris Fuller wrote:

> This is a classic case for the use of regular expressions.  A powerful tool, 
> but can be tricky.  I create a RE for a record, and than use the findall() 
> function to get all of them in a list.  I'll walk you through it.

> # seperate into records
> lin = re.findall('\s*([^\s]+)\s+([^\s]+)\s+(\d+)( [kM])?bytes', s)

This is just splitting on whitespace, you could just use s.split().

> # now sort
> lout.sort(lambda a,b: cmp(a[2], b[2]))

> The other tricky bit is the sort.  In python, lists can be sorted in place, if 
> you pass a function that determines the relative precedence of two elements.  

Recent versions of Python have a better (faster, easier to understand) 
way to do this using the key parameter to sort. The above could be 
written as

lout.sort(key=lambda a: a[2])

or, better:
import operator
lout.sort(key=operator.itemgetter(2))

Kent