[Tutor] Counting & Sorting Instances In File

[Michael Barrett]

Thanks for all your help with this.  :)

On Wed, May 14, 2003 at 06:59:43PM -0700, Jeff Shannon wrote:
> Michael Barrett wrote:
> 
> >   The hard (?) part is the sorting.  Thats the part I need help with, so 
> >   assume a dictionary of 'Email': count values.  If you can think of a 
> >   better way of storing the data in memory for my sort, that'd be 
> >   appreciated as well.  Thanks again.
> >
> 
> Doing your counting *is* best done with a dictionary, especially if you 
> make use of the get() method --
> 
> for line in logfile:
>    email = parse_email_addr(line)
>    emailcount[email] = emailcount.get(email, 0) + 1
> 
> Once you have that dictionary of email:count values, you can convert 
> that to a list and use the list's built-in sort() method.  When sorting 
> a list where each element is another list (or a tuple), the first 
> element of the nested list is used to sort on, so the best thing to do 
> is to ensure that that first element is your count.
> 
> # first, use a list comprehension to create a list of (count, email) pairs
> email_list = [ (value, key) for key, value in emailcount.items() ]
> # now sort the list
> email_list.sort()
> # to sort from highest count to lowest count, reverse the list
> email_list.reverse()
> # now print the first 25
> for count, email in email_list[:25]:
>    print "%25s     %d"  % (email, count)
> 
> If there's any of this that doesn't make sense, I can explain in a 
> little more detail...
> 
> Jeff Shannon
> Technician/Programmer
> Credit International
> 
> 
> 
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