Suppressing newline writing to file after variable

Ellerbee, Edward EEllerbee at BBandT.com
Thu Jul 14 16:53:23 CEST 2011


Holy cow, that's perfect!

Thanks so much :) 

Would it be alright if I post my code on the list for critiquing? I'm
learning python to supplement my voice engineering position - time
consuming tasks that can be automated will take less time.


Edward Ellerbee


-----Original Message-----
From: python-list-bounces+eellerbee=bbandt.com at python.org
[mailto:python-list-bounces+eellerbee=bbandt.com at python.org] On Behalf
Of Chris Angelico
Sent: Thursday, July 14, 2011 10:39 AM
To: python-list at python.org
Subject: Re: Suppressing newline writing to file after variable

On Fri, Jul 15, 2011 at 12:04 AM, Ellerbee, Edward
<EEllerbee at bbandt.com> wrote:
> Hey Chris,
>
> I was reading over this again, trying to understand the logic (I'm a
> n00b)
>
> Could you explain this a bit? I'd like to build this emit function, 
> but I still don't have a firm grasp on functions. All of my code is 
> line by line. I'll convert it as a learn more.

I'm responding on-list as I believe others will wish to weigh in (if
only to point out some improvements to my code - it's hastily put
together). Caution, post is long.

Defining functions in Python is, broadly speaking, just a matter of
collecting up a bunch of statements and giving it a name. Compare:

if x>5:
   do_this()
   do_that()
   etc()

with:

def abcde():
   do_this()
   do_that()
   etc()

The first one does the three statements, in order, if and only if the
condition is true. The second one gives a name to those three
statements, so you can use it as a new statement:

abcde()

It'll do the same three things, every time you call it. It's effectively
the same as putting the function's body in where you call it (that's an
extremely sloppy explanation, but near enough).

> So, I'd want this to go after the sort step, and before the format
step.
> I can figure that piece out, just trying to get this little block of 
> code to work.

Yes, that would be the place to put it.

Here's a reworked version that you can test in IDLE:


def combine(list_of_numbers, position):
 lastprefix=tails=lastsuffix=None
 result=[]
 for cur in list_of_numbers:
  prefix=cur[:position]; tail=cur[position]; suffix=cur[position+1:]
  if prefix!=lastprefix or suffix!=lastsuffix:
   if lastprefix!=None:
    if len(tails)>1:
result.append("%s[%s]%s"%(lastprefix,tails,lastsuffix))
    else: result.append(lastprefix+tails+lastsuffix)
   lastprefix,tails,lastsuffix=prefix,"",suffix
  tails+=tail
 if lastprefix!=None:
  if len(tails)>1:
result.append("%s[%s]%s"%(lastprefix,tails,lastsuffix))
  else: result.append(lastprefix+tails+lastsuffix)
 return result

It incorporates some of the enhancements I mentioned in the original
post.

>>> combine(['252205','252206','252208'],5)
['25220[568]']
>>> combine(['252205','252215','252225'],4)
['2522[012]5']

Notice that the 'emit' function is now 'result.append()' - it builds up
a list to return. You can now chain the calls; start with a list of
numbers and then call combine() in a loop.

# List of numbers from your previous post numbers = ['252205', '252206',
'252208', '252220', '252221', '252222', '252223', '919745', '919725',
'919785', '704770', '704771', '704772', '704773', '704774', '704775',
'704776', '704777', '704778', '704779', '704780', '704781', '704782',
'704783', '704784', '704785', '704786', '704787', '704788', '704789',
'704790', '704791', '704792', '704793', '704794', '704795', '704796',
'704797', '704798', '704799']


numbers = combine(numbers,5)

numbers = combine(numbers,4)

numbers = combine(numbers,3)

numbers = combine(numbers,2)

numbers = combine(numbers,1)

numbers = combine(numbers,0)

If you do these statements one at a time in IDLE and inspect the
'numbers' list each time, you'll see the combinations sorting themselves
out. (With this starting list, only the first two will have any effect.)

The last set of calls can be turned into a for loop:
for pos in range(5,-1,-1):
   numbers = combine(numbers,pos)

In fact, you could actually take it out of being a function, if you
wanted to:

list_of_numbers = ['252205', '252206', '252208', '252220', '252221',
'252222', '252223', '919745', '919725', '919785', '704770', '704771',
'704772', '704773', '704774', '704775', '704776', '704777', '704778',
'704779', '704780', '704781', '704782', '704783', '704784', '704785',
'704786', '704787', '704788', '704789', '704790', '704791', '704792',
'704793', '704794', '704795', '704796', '704797', '704798', '704799']

for position in range(5,-1,-1):
 lastprefix=tails=lastsuffix=None
 result=[]
 for cur in list_of_numbers:
  prefix=cur[:position]; tail=cur[position]; suffix=cur[position+1:]
  if prefix!=lastprefix or suffix!=lastsuffix:
   if lastprefix!=None:
    if len(tails)>1:
result.append("%s[%s]%s"%(lastprefix,tails,lastsuffix))
    else: result.append(lastprefix+tails+lastsuffix)
   lastprefix,tails,lastsuffix=prefix,"",suffix
  tails+=tail
 if lastprefix!=None:
  if len(tails)>1:
result.append("%s[%s]%s"%(lastprefix,tails,lastsuffix))
  else: result.append(lastprefix+tails+lastsuffix)
 list_of_numbers = result

That's what the function definition does - it takes a block of code and
gives it a new name. (There's a lot more to it than that, thank you
pedants I know, but in this simple example that's what it's
doing.)

Hope that's of use!

Chris Angelico
--
http://mail.python.org/mailman/listinfo/python-list




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