sorting tuples...

[nidhog]

Hello guys,

I made a script that extracts strings from a binary file. It works.

My next problem is sorting those strings.

Output is like:

---- snip ----
200501221530
John
*** long string here ***

200504151625
Clyde
*** clyde's long string here ***

200503130935
Jeremy
*** jeremy string here ****
---- snip ----

How can I go about sorting this list based on the date string that
marks the start of each message?

Should I be using lists, dictionaries or tuples?

What should I look into?

Is there a way to generate variables in a loop? Like:

x=0
while (x<10):
# assign variable-x = [...list...]
x = x+1

Thanks.

 

[bearophileHUGS]

Uhm, if the file is clean you can use something like this:

data = """\
200501221530
John
*** long string here ***

200504151625
Clyde
*** clyde's long string here ***

200503130935
Jeremy
*** jeremy string here ****"""

records = [rec.split("\n") for rec in data.split("\n\n")]
records.sort()
print records

If it's not clean, you have to put some more cheeks/cleanings.

Bye,
bearophile

 

[Bengt Richter]

Hello guys,

I made a script that extracts strings from a binary file. It works.

My next problem is sorting those strings.

Output is like:

---- snip ----
200501221530
John
*** long string here ***

200504151625
Clyde
*** clyde's long string here ***

200503130935
Jeremy
*** jeremy string here ****
---- snip ----

How can I go about sorting this list based on the date string that
marks the start of each message?

Should I be using lists, dictionaries or tuples?

What should I look into?

Is there a way to generate variables in a loop? Like:

x=0
while (x<10):
# assign variable-x = [...list...]
x = x+1

Thanks.

Assuming your groups of strings are all non-blank lines delimited by blank lines,
and using StringIO as a line iterable playing the role of your source of lines,
(not tested beyond what you see ;-)
... 200501221530
... John
... *** long string here ***
...
... 200504151625
... Clyde
... *** clyde's long string here ***
...
... 200503130935
... Jeremy
... *** jeremy string here ****
... """) ... lambda line:line.strip()!='') if k):
... print t
...
('200501221530\n', 'John\n', '*** long string here ***\n')
('200503130935\n', 'Jeremy\n', '*** jeremy string here ****\n')
('200504151625\n', 'Clyde\n', "*** clyde's long string here ***\n")

The lambda computes a grouping key that groupby uses to collect group members
as long as the value doesn't change, so this groups non-blank vs blank lines,
and the "if k" throws out the blank-line groups.

Obviously you could do something else with the sorted line tuples t, e.g.,
(just needed that to rewind the StringIO data here)
... lambda line:line.strip()!='') if k):
... width = max(map(lambda x:len(x.rstrip()), t))
... topbot = '+-%s-+'%('-'*width)
... print topbot
... for line in t: print '| %s |' % line.rstrip().ljust(width)
... print topbot
... print
...
+--------------------------+
| 200501221530 |
| John |
| *** long string here *** |
+--------------------------+

+-----------------------------+
| 200503130935 |
| Jeremy |
| *** jeremy string here **** |
+-----------------------------+

+----------------------------------+
| 200504151625 |
| Clyde |
| *** clyde's long string here *** |
+----------------------------------+

Or of course you can just print the sorted groups bare:
... lambda line:line.strip()!='') if k):
... print ''.join(t)
...
200501221530
John
*** long string here ***

200503130935
Jeremy
*** jeremy string here ****

200504151625
Clyde
*** clyde's long string here ***

If your source of line groups is not delimited by blank lines,
or has other non-blank lines, you will have to change the source
or change the lambda to some other key function that produces one
value for the lines to include (True if you want to use if k as above)
and another (False) for the ones to exclude.

HTH

Regards,
Bengt Richter

 

[nidhog]

Thank you very much.

I'll look into this immediately.

I edited my code earlier and came up with stringing the groups
(200501202010, sender, message_string) into one string delimited by
'%%%'.

I could then sort the messages with the date string at the beginning as
the one being sorted with the big string in its "tail" being sorted
too.

200501202010%%%sender%%%message_string
200502160821%%%sender%%%message_string
....

After sorting this list of long strings, I could then split them up
using the '%%%' delimiter and arrange them properly for output.

It's crude but at least I achieve what I wanted done.

But both posters gave good advices, if not a bit too advanced for me.
I'll play with them and keep tweaking my code.

Thanks so much!

 

[Magnus Lycka]

I edited my code earlier and came up with stringing the groups
(200501202010, sender, message_string) into one string delimited by
'%%%'.

Why? It seems you are trying to use a string as some kind of container,
and Python has those in the box. Just use a list of tuples, rather than
a list of strings. That will work fine for .sort(), and it's much more
convenient to access your data. Using the typical tool for extracting
binary data from files/strings will give you tuples by default.
"200501221530John *** long string here *** "
"200504151625Clyde *** clyde's long string here ***"
"200503130935Jeremy *** jeremy string here **** ")

>>> fmt="@12s8s32s" # imagined binary format.
>>> l=52 # 12+8+32, from previous line
>>> msgs = []
>>> for i in range(3):

.... # struct.unpack will return a tuple. It works well
.... # with numeric data too.
.... msgs.append(struct.unpack(fmt, bin[i*li+1)*l]))
.... print msg

('200501221530', 'John ', '*** long string here *** ')
('200503130935', 'Jeremy ', '*** jeremy string here **** ')
('200504151625', 'Clyde ', "*** clyde's long string here ***")

I could then sort the messages with the date string at the beginning as
the one being sorted with the big string in its "tail" being sorted
too.

This works equally well with a list of tuples. Another benefit of
the list of tuples approach is that you don't need to cast everything
to strings. If parts of your data is e.g. numeric, just let it be an
int, a long or a float in your struct, and sorting will work correctly
without any need to format the number in such a way as to make string
sorting work exactly as numeric sorting.

Here's an example with numeric data:
'\x00\x00\x07\xd5\x00\x00\x00\x01\x00\x00\x00\x16\x00\x00\x00'
'\x0f\x00\x00\x00\x1eJohn\x00\x00\x00\x00*** long string here'
' ***\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x07\xd5\x00\x00'
'\x00\x03\x00\x00\x00\r\x00\x00\x00\t\x00\x00\x00#Jeremy\x00'
'\x00*** jeremy string here ****\x00\x00\x00\x00\x00\x00\x00'
'\x07\xd5\x00\x00\x00\x04\x00\x00\x00\x0f\x00\x00\x00\x10\x00'
'\x00\x00\x19Clyde\x00\x00\x00*** clyde\'s long string here ***')

>>> fmt="!iiiii8s32s"
>>> l = 60 # five ints (5*4) + 8 + 32
>>> bin_msgs=[]
>>> for i in range(3):

bin_msgs.append(struct.unpack(fmt, bin[i*li+1)*l]))

print msg


(2005, 1, 22, 15, 30, 'John\x00\x00\x00\x00', '*** long string here
***\x00\x00\x00\x00\x00\x00\x00\x00')
(2005, 3, 13, 9, 35, 'Jeremy\x00\x00', '*** jeremy string here
****\x00\x00\x00\x00\x00')
(2005, 4, 15, 16, 25, 'Clyde\x00\x00\x00', "*** clyde's long string here
***")

 

[nidhog]

Why? It seems you are trying to use a string as some kind of container,
and Python has those in the box. Just use a list of tuples, rather than
a list of strings. That will work fine for .sort(), and it's much more
convenient to access your data. Using the typical tool for extracting
binary data from files/strings will give you tuples by default.

my problem with tuples & lists is that i don't know how to assign data
to them properly. i'm quite new in python

with the binary stuff out of the way, what i have is this string data:

20050922 # date line
mike
mike's message...
20040825 # date line
jeremy
jeremy's message...
....

what i want to do is to use the date line as the first data in a tuple
and the succeeding lines goes into the tuple, like:

(20050922, mike, mike's message)

then when it matches another date line it makes another new tuple with
that date line as the header data and the succeeding data, etc..

(20050922, mike, mike's message)
(20040825, jeremy, jeremy's message)
....

then i would sort the tuples according to the date.

is there an easier/proper way of doing this without generating alot of
tuples?

thanks! for the help

 

[Dan Sommers]

On 27 Sep 2005 19:01:38 -0700,

with the binary stuff out of the way, what i have is this string data:

20050922 # date line
mike
mike's message...
20040825 # date line
jeremy
jeremy's message...
...

what i want to do is to use the date line as the first data in a tuple
and the succeeding lines goes into the tuple, like:

(20050922, mike, mike's message)

then when it matches another date line it makes another new tuple with
that date line as the header data and the succeeding data, etc..

(20050922, mike, mike's message)
(20040825, jeremy, jeremy's message)
...

then i would sort the tuples according to the date.

is there an easier/proper way of doing this without generating alot of
tuples?

You want a dictionary. Python dictionaries map keys to values (in other
languages, these data structures are known as hashes, maps, or
associative arrays). The keys will be the dates; the values will depend
on whether or not you have multiple messages for one date.

If the dates are unique (which, looking at your data, is probably not
true), then each item in the dictionary can be just one (who, message)
tuple.

If the dates are not unique, then you'll have to manage each item of the
dictionary as a list of (who, message) tuples.

And before you ask: no, dictionaries are *not* sorted; you'll have to
sort a separate list of the keys or the items at the appropriate time.

Regards,
Dan

 

[Steve Holden]

On 27 Sep 2005 19:01:38 -0700,



You want a dictionary. Python dictionaries map keys to values (in other
languages, these data structures are known as hashes, maps, or
associative arrays). The keys will be the dates; the values will depend
on whether or not you have multiple messages for one date.

If the dates are unique (which, looking at your data, is probably not
true), then each item in the dictionary can be just one (who, message)
tuple.

If the dates are not unique, then you'll have to manage each item of the
dictionary as a list of (who, message) tuples.

And before you ask: no, dictionaries are *not* sorted; you'll have to
sort a separate list of the keys or the items at the appropriate time.

I'm not sure this advice is entirely helpful, since it introduces
complexities not really required by the simplistic tuple notation the OP
seems to be struggling for.

Following the old adage "First, make it work; then (if it doesn't work
fast enough) make it faster)", and making the *dangerous* assumption
that each message genuinely is exactly three lines, we might write:

msglist = []
f = open("theDataFile.txt", "r")
for date in f:
who = f.next() # pulls a line from the file
msg = f.next() # pulls a line from the file
msglist,append((date, who, msg))
# now have list of messages as tuples
msglist.sort()

After this, msglist should be date-sorted list of messages. Though who
knows what needs to happen to them next ...

regards
Steve

 

[nidhog]

On 27 Sep 2005 19:01:38 -0700,



You want a dictionary. Python dictionaries map keys to values (in other
languages, these data structures are known as hashes, maps, or
associative arrays). The keys will be the dates; the values will depend
on whether or not you have multiple messages for one date.

If the dates are unique (which, looking at your data, is probably not
true), then each item in the dictionary can be just one (who, message)
tuple.

If the dates are not unique, then you'll have to manage each item of the
dictionary as a list of (who, message) tuples.

And before you ask: no, dictionaries are *not* sorted; you'll have to
sort a separate list of the keys or the items at the appropriate time.

I'm not sure this advice is entirely helpful, since it introduces
complexities not really required by the simplistic tuple notation the OP
seems to be struggling for.

Following the old adage "First, make it work; then (if it doesn't work
fast enough) make it faster)", and making the *dangerous* assumption
that each message genuinely is exactly three lines, we might write:

msglist = []
f = open("theDataFile.txt", "r")
for date in f:
who = f.next() # pulls a line from the file
msg = f.next() # pulls a line from the file
msglist,append((date, who, msg))
# now have list of messages as tuples
msglist.sort()

After this, msglist should be date-sorted list of messages. Though who
knows what needs to happen to them next ...

just to spit it all out to stdout in a nice formatted form so I can
save it to a file.

I'm still confused though, but I'm working on it. struct is nice.