Lining Up and PaddingTwo Similar Lists

[W. eWatson]

Maybe there's some function like zip or map that does this. If not, it's
probably fairly easy to do with push and pop. I'm just checking to see if
there's not some known simple single function that does what I want. Here's
what I'm trying to do.

I have a list dat like (assume the items are strings even thought I'm
omitting quotes.):
[a.dat, c.dat, g.dat, k.dat, p.dat]

I have another list called txt that looks like:
[a.txt, b.txt, g.txt, k.txt r.txt, w.txt]

What I need is to pair up items with the same prefix and use "None", or some
marker, to indicate the absence of the opposite item. That is, in non-list
form, I want:
a.dat a.txt
None b.txt
c.dat None
g.dat g.txt
k.dat k.txt
p.dat None
None r.txt
None w.txt

Ultimately, what I'm doing is to find the missing member of pairs.
--
Wayne Watson (Watson Adventures, Prop., Nevada City, CA)

(121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std. time)
Obz Site: 39° 15' 7" N, 121° 2' 32" W, 2700 feet

Web Page: <www.speckledwi thstars.net/>

[castironpi]

Re: Lining Up and PaddingTwo Similar Lists

On Aug 28, 10:50 pm, "W. eWatson" <notval...@sbcg lobal.netwrote:

Maybe there's some function like zip or map that does this. If not, it's
probably fairly easy to do with push and pop. I'm just checking to see if
there's not some known simple single function that does what I want. Here's
what I'm trying to do.
>
I have a list dat like (assume the items are strings even thought I'm
omitting quotes.):
[a.dat, c.dat, g.dat, k.dat, p.dat]
>
I have another list called txt that looks like:
[a.txt, b.txt, g.txt, k.txt r.txt, w.txt]
>
What I need is to pair up items with the same prefix and use "None", or some
marker, to indicate the absence of the opposite item. That is, in non-list
form, I want:
a.dat a.txt
None  b.txt
c.dat None
g.dat g.txt
k.dat k.txt
p.dat  None
None  r.txt
None  w.txt
>
Ultimately, what I'm doing is to find the missing member of pairs.
--
            Wayne Watson (Watson Adventures, Prop., Nevada City, CA)
>
              (121.015 Deg. W, 39.262 Deg. N) GMT-8 hr std.time)
               Obz Site:  39° 15' 7" N, 121° 2' 32"W, 2700 feet
>
                     Web Page: <www.speckledwi thstars.net/>

This gets you your list. What do you mean by 'missing member of
pairs'? If you mean, 'set of elements that appear in both' or 'set
that appears in one but not both', you can short circuit it at line
14.

-warning, spoiler-

dat= ['a.dat', 'c.dat', 'g.dat', 'k.dat', 'p.dat']
dat.sort()
txt= ['a.txt', 'b.txt', 'g.txt', 'k.txt', 'r.txt', 'w.txt']
txt.sort()
import os.path
datD= {}
for d in dat:
r,_= os.path.splitex t( d )
datD[ r ]= d
txtD= {}
for d in txt:
r,_= os.path.splitex t( d )
txtD[ r ]= d
both= sorted( list( set( datD.keys() )| set( txtD.keys() ) ) )

print datD
print txtD
print both

for i, x in enumerate( both ):
both[ i ]= datD.get( x, None ), txtD.get( x, None )

print both

OUTPUT:

{'a': 'a.dat', 'p': 'p.dat', 'c': 'c.dat', 'k': 'k.dat', 'g': 'g.dat'}
{'a': 'a.txt', 'b': 'b.txt', 'g': 'g.txt', 'k': 'k.txt', 'r': 'r.txt',
'w': 'w.t
xt'}
['a', 'b', 'c', 'g', 'k', 'p', 'r', 'w']
[('a.dat', 'a.txt'), (None, 'b.txt'), ('c.dat', None), ('g.dat',
'g.txt'), ('k.d
at', 'k.txt'), ('p.dat', None), (None, 'r.txt'), (None, 'w.txt')]

[Paul Rubin]

Re: Lining Up and PaddingTwo Similar Lists

"W. eWatson" <notvalid2@sbcg lobal.netwrites :

[a.dat, c.dat, g.dat, k.dat, p.dat]
[a.txt, b.txt, g.txt, k.txt r.txt, w.txt]
>
What I need is to pair up items with the same prefix and use "None",
or some marker, to indicate the absence of the opposite item.

This is functionally influenced but should be straightforward :

dat = ['a.dat', 'c.dat', 'g.dat', 'k.dat', 'p.dat']
txt = ['a.txt', 'b.txt', 'g.txt', 'k.txt', 'r.txt', 'w.txt']

# just get the portion of the filename before the first period
def prefix(filename ):
return filename[:filename.find( '.')]

# make a dictionary mapping prefixes to filenames
def make_dict(plist ):
return dict((prefix(a) ,a) for a in plist)

pdat = make_dict(dat)
ptxt = make_dict(txt)

# get a list of all the prefixes, use "set" to remove
# duplicates, then sort the result and look up each prefix.
for p in sorted(set(pdat .keys() + ptxt.keys())):
print pdat.get(p), ptxt.get(p)

[Boris Borcic]

Re: Lining Up and PaddingTwo Similar Lists

D,T=[dict((x.split(' .')[0],x) for x in X) for X in (dat,txt)]
for k in sorted(set(D).u nion(T)) :
for S in D,T :
print '%-8s' % S.get(k,'None') ,
print

HTH

W. eWatson wrote:

Maybe there's some function like zip or map that does this. If not, it's
probably fairly easy to do with push and pop. I'm just checking to see
if there's not some known simple single function that does what I want.
Here's what I'm trying to do.
>
I have a list dat like (assume the items are strings even thought I'm
omitting quotes.):
[a.dat, c.dat, g.dat, k.dat, p.dat]
>
I have another list called txt that looks like:
[a.txt, b.txt, g.txt, k.txt r.txt, w.txt]
>
What I need is to pair up items with the same prefix and use "None", or
some marker, to indicate the absence of the opposite item. That is, in
non-list form, I want:
a.dat a.txt
None b.txt
c.dat None
g.dat g.txt
k.dat k.txt
p.dat None
None r.txt
None w.txt
>
Ultimately, what I'm doing is to find the missing member of pairs.

[W. eWatson]

Re: Lining Up and PaddingTwo Similar Lists

castironpi wrote:
....

>
I don't think that's guaranteed by anything. I realized that
'dat.sort()' and 'txt.sort()' weren't necessary, since their contents
are moved to a dictionary, which isn't sorted.

Actually, I'm getting the file names from listdir, and they appear to be
sorted low to high. I tried it on a folder with lots of dissimilar files.

>
both= set( datD.keys() )& set( txtD.keys() )
>
This will get you the keys (prefixes) that are in both. Then for
every prefix if it's not in 'both', you can report it.
>
Lastly, since you suggest you're guaranteed that 'txt' will all share
the same extension, you can do away with the dictionary and use sets
entirely. Only if you can depend on that assumption.

Each dat file contains an image, and its description and related parameters
are in the corresponding txt file.

>
I took a look at this. It's probably more what you had in mind, and
the dictionaries are overkill.

....

[George Sakkis]

Re: Lining Up and PaddingTwo Similar Lists

On Aug 29, 1:29 am, "W. eWatson" <notval...@sbcg lobal.netwrote:

It looks like I have a few new features to learn about in Python. In particular,
dictionaries.

In Python it's hard to think of many non-trivial problems that you
*don't* have to know about dictionaries.

George