Re: [Tutor] Unique Items in Lists
for i in range(len(a)): for k in range(len(a)): for k in range(i,len(a)): is faster, and if you calculate len before starting the loops that will speed it up too. (You calculate len for each iteration of each loop!) if i != k: if a[i] == a[k]: print a[i] break HTH Alan G. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Unique Items in Lists
Dear Danny, thank you for ur help. But a basic
question ?
In a table, more specifically a matrix 3X3,
AppleFruitDenmark
F-16 Fighter USA
Taj Wonder India
MummyAntique Egypt
IF I have to sort on country, it should be
AppleFruitDenmark
MummyAntique Egypt
Taj Wonder India
F-16 Fighter USA
How can I sort by binding Denmark to fruit and apple
as a string. String does not support sort function.
Sincerly I dont know how to sort to follow your
suggestion. can you please help.. sorry for asking
basic question.
thank you
--- Danny Yoo [EMAIL PROTECTED] wrote:
On Wed, 26 Jan 2005, Srinivas Iyyer wrote:
I have a list with 4 columns and column1 elements
are unique. I wanted
to extract unique elements in column3 and and
place the other elements
of the column along with unique elements in column
4 as a tab delim
text.
Table:
col1col2col3 col4
A Apple 5Chennai
B Baby 11Delhi
I Baby* 1Delhi
M Dasheri+ 5Mumbai
K Apple 12 Copenhagen
[Meta: we seem to be getting a run of similar
questions this week. Scott
Melnyk also asked about grouping similar records
together:
http://mail.python.org/pipermail/tutor/2005-January/035185.html.]
Hi Srinivas,
I see that you are trying to group records based on
some criterion. You
may find the problem easier to do if you fist do a
sort on that criterion
column: that will make related records clump
together.
For your sample data above, if we sort against the
second column, the
records will end up in the following order:
###
A Apple 5Chennai
K Apple 12 Copenhagen
B Baby 11 Delhi
I Baby 1Delhi
M Dasheri 5Mumbai
###
In this sorting approach, you can then run through
the sorted list in
order. Since all the related elements should be
adjacent, grouping
related lines together should be much easier, and
you should be able to
produce the final output:
###
Apple A,K 5,12Chennai,Copenhagen
Baby B,I 1,11Delhi
Dasheri M 5 Mumbai
###
without too much trouble. You can do this problem
without dictionaries at
all, although you may find the dictionary approach a
little easier to
implement.
A dictionary option does not work
A dictionary approach is also very possible. The
thing you may be stuck
on is trying to make a key associate with multiple
values. Most examples
of dictionaries in tutorials use strings as both the
keys and values, but
dictionaries are more versatile: we can also make a
dictionary whose
values are lists.
For example, here is a small program that groups
words by their first
letters:
###
def groupAlpha(words):
... groups = {}
... for w in words:
... firstLetter = w[0]
... if firstLetter not in groups:
... groups[firstLetter] = []
... groups[firstLetter].append(w)
... return groups
...
groupAlpha(this is a test of the emergency
broadcast system.split())
{'a': ['a'],
'b': ['broadcast'],
'e': ['emergency'],
'i': ['is'],
'o': ['of'],
's': ['system'],
't': ['this', 'test', 'the']}
###
If you have more questions, please feel free to ask.
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Re: [Tutor] Unique Items in Lists
Srinivas,
You can't sort a string, since it's immutable. You can, however, sort
a list. To sort your table by the third element, you can do something
like this:
table = ((apple, fruit, denmark),
... (mummy, antique, egypt),
... (taj, wonder, india),
... (f-16, fighter, usa))
sorter = [(elt[2], elt) for elt in table]
sorter.sort()
tuple([elt[1] for elt in sorter])
(('apple', 'fruit', 'denmark'),
('mummy', 'antique', 'egypt'),
('taj', 'wonder', 'india'),
('f-16', 'fighter', 'usa'))
# I edited the table output edited for clarity
When you sort a list of tuples, the default is to sort the list by the
first element in the tuples. If you make a list where the element you
want to sort on is first in all of the tuples (see the 'sorter = ...'
line), then sort that list, then remove the element you added (the
'tuple([...])' line), you are left with a list which is ordered the
way you want it.
Peace
Bill Mill
bill.mill at gmail.com
On Thu, 27 Jan 2005 08:29:10 -0800 (PST), Srinivas Iyyer
[EMAIL PROTECTED] wrote:
Dear Danny, thank you for ur help. But a basic
question ?
In a table, more specifically a matrix 3X3,
AppleFruitDenmark
F-16 Fighter USA
Taj Wonder India
MummyAntique Egypt
IF I have to sort on country, it should be
AppleFruitDenmark
MummyAntique Egypt
Taj Wonder India
F-16 Fighter USA
How can I sort by binding Denmark to fruit and apple
as a string. String does not support sort function.
Sincerly I dont know how to sort to follow your
suggestion. can you please help.. sorry for asking
basic question.
thank you
--- Danny Yoo [EMAIL PROTECTED] wrote:
On Wed, 26 Jan 2005, Srinivas Iyyer wrote:
I have a list with 4 columns and column1 elements
are unique. I wanted
to extract unique elements in column3 and and
place the other elements
of the column along with unique elements in column
4 as a tab delim
text.
Table:
col1col2col3 col4
A Apple 5Chennai
B Baby 11Delhi
I Baby* 1Delhi
M Dasheri+ 5Mumbai
K Apple 12 Copenhagen
[Meta: we seem to be getting a run of similar
questions this week. Scott
Melnyk also asked about grouping similar records
together:
http://mail.python.org/pipermail/tutor/2005-January/035185.html.]
Hi Srinivas,
I see that you are trying to group records based on
some criterion. You
may find the problem easier to do if you fist do a
sort on that criterion
column: that will make related records clump
together.
For your sample data above, if we sort against the
second column, the
records will end up in the following order:
###
A Apple 5Chennai
K Apple 12 Copenhagen
B Baby 11 Delhi
I Baby 1Delhi
M Dasheri 5Mumbai
###
In this sorting approach, you can then run through
the sorted list in
order. Since all the related elements should be
adjacent, grouping
related lines together should be much easier, and
you should be able to
produce the final output:
###
Apple A,K 5,12Chennai,Copenhagen
Baby B,I 1,11Delhi
Dasheri M 5 Mumbai
###
without too much trouble. You can do this problem
without dictionaries at
all, although you may find the dictionary approach a
little easier to
implement.
A dictionary option does not work
A dictionary approach is also very possible. The
thing you may be stuck
on is trying to make a key associate with multiple
values. Most examples
of dictionaries in tutorials use strings as both the
keys and values, but
dictionaries are more versatile: we can also make a
dictionary whose
values are lists.
For example, here is a small program that groups
words by their first
letters:
###
def groupAlpha(words):
... groups = {}
... for w in words:
... firstLetter = w[0]
... if firstLetter not in groups:
... groups[firstLetter] = []
... groups[firstLetter].append(w)
... return groups
...
groupAlpha(this is a test of the emergency
broadcast system.split())
{'a': ['a'],
'b': ['broadcast'],
'e': ['emergency'],
'i': ['is'],
'o': ['of'],
's': ['system'],
't': ['this', 'test', 'the']}
###
If you have more questions, please feel free to ask.
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Re: [Tutor] Unique Items in Lists
Ok. I think I understand and I happen to be up at 1:30 my time so
here
is the solution as I understand the problem. This is a very common
problem and has a fairly easy solution. You can then take
adict.keys()
which returns a list of unique elements. Good Luck
import random
l=[random.randrange(1,20) for x in range(100)]
l
[7, 18, 17, 17, 6, 11, 14, 9, 4, 16, 2, 9, 3, 13, 4, 2, 5, 15, 15, 3,
3,
11, 18, 12, 6, 8, 15, 3, 7, 9, 9, 7, 12, 11, 11, 9, 19, 19, 15, 2,
17,
18, 16, 8, 15, 3, 19, 19, 19, 1, 3, 17, 3, 8, 16, 1, 5, 19, 17, 16,
19,
6, 3, 8, 16, 11, 12, 7, 10, 13, 13, 11, 6, 2, 18, 15, 17, 8, 12, 13,
5,
12, 2, 19, 2, 19, 7, 10, 4, 14, 15, 14, 5, 1, 16, 1, 9, 10, 17, 12]
adict={}
for x in l:
if adict.has_key(x):
#then there is already an item
adict[x]+=1 #increment the count by one
else: #there is no key the item hasn't been seen
adict[x]=1 #there is one instance so far
adict
{1: 4, 2: 6, 3: 8, 4: 3, 5: 4, 6: 4, 7: 5, 8: 5, 9: 6, 10: 3, 11: 6,
12:
6, 13: 4, 14: 3, 15: 7, 16: 6, 17: 7, 18: 4, 19: 9}
Srinivas Iyyer wrote:
Dear Jacob, thank you for your suggestion.
however, i think my question was not clear. what i
meant to ask in my previous question was, how to know
which elements repeated and how many times they were
repeated.
while my question was flying, i did a small test:
took a list:
a
[1, 1, 2, 3, 4, 2, 2]
wanted to know which elements repeated and how many
times:
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Re: [Tutor] Unique Items in Lists
Srinivas Iyyer said unto the world upon 2005-01-27 01:17:
Dear Jacob, thank you for your suggestion.
however, i think my question was not clear. what i
meant to ask in my previous question was, how to know
which elements repeated and how many times they were
repeated.
while my question was flying, i did a small test:
took a list:
a
[1, 1, 2, 3, 4, 2, 2]
wanted to know which elements repeated and how many
times:
for i in range(len(a)):
for k in range(len(a)):
if i != k:
if a[i] == a[k]:
print a[i]
break
SNIP
In this very huge list (:-) kidding) of 7 elements, it
is easy know by the above primitive code that there 1
s repeated two times, and 2 s repeated three times and
finally 1 and 2 numbers are repeated in list a:
With sets option i get a list of unique elements, but
by no means i get to know which elements were repeated
and how many times. With the above primitive code , I
know that 1 and 2 are peated. However, in case where
there are thousands of entries, how can I get to kno
wich elements got repeated and how many times.
Do you see any flaws in this code, how can that be
made to look more pyhonian way.
Hope my question is clear now and appreciate your
suggestions.
Thank you in advance
Srini
SNIP
Hi Srini,
for the task of finding out which items are repeated and how many
times, I'd do this:
code
def dups_in_list_report(a_list):
'''Prints a duplication report for a list.'''
items_dict = {}
for i in a_list:
if i in items_dict:
items_dict[i] = items_dict[i] + 1
else:
items_dict[i] = 1
for key in items_dict.copy(): # Try it without the .copy()
if items_dict[key] == 1:# and see what happens.
del items_dict[key]
dict_keys = items_dict.keys()
dict_keys.sort()
for key in dict_keys:
print '%s occurred %s times' %(key, items_dict[key])
f = [1,1,2,3,3,3,3,4,4,4,4,4,4,4,5]
dups_in_list_report(f)
/code
And, now that I get back on-line, I see that Chad posted the same
basic idea. But, perhaps the extra stuff here is of use, too.
HTH,
Brian vdB
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