Note that dictionary keys are not ordered, so--if I understand your
requirement correctly--it could also result in {'ba': [3, 4, 5, 1,
2]}.
> Now i want to check each pair to see if they are connected...element of
> this pair will be one from the first list and one from the second....e.g
> for 'ab' i want to check if 1 and 3 are connected,then 1 and 4,then 1 and
> 5,then 2 and 3,then 2 and 4,then 2 and 5.
According to this, I think that you shouldn't concatenate the lists,
but keep them apart instead.
> The information of this connected thing is in a text file as follows:
> 1,'a',2,'b'
> 3,'a',5,'a'
> 3,'a',6,'a'
> 3,'a',7,'b'
> 8,'a',7,'b'
> .
> This means 1(type 'a') and 2(type 'b') are connected,3 and 5 are connected
> and so on.
> I am not able to figure out how to do this.Any pointers would be helpful
I don't understand very well what you want to do. Could you explain
it more clearly, with an example?
--
Roberto Bonvallet
Girish
It seems you want the Cartesian product of every pair of lists in the
dictionary, including the product of lists with themselves (but you
don't say why ;-)).
I'm not sure the following is exactly what you want or if it is very
efficient, but maybe it will start you off. It uses a function
'xcombine' taken from a recipe in the ASPN cookbook by David
Klaffenbach (2004).
(It should give every possibility, which you then check in your file)
Gerard
-------------------------------------------------------------------------
def nkRange(n,k):
m = n - k + 1
indexer = range(0, k)
vector = range(1, k+1)
last = range(m, n+1)
yield vector
while vector != last:
high_value = -1
high_index = -1
for i in indexer:
val = vector[i]
if val > high_value and val < m + i:
high_value = val
high_index = i
for j in range(k - high_index):
vector[j+high_index] = high_value + j + 1
yield vector
def kSubsets( alist, k ):
n = len(alist)
for vector in nkRange(n, k):
ret = []
for i in vector:
ret.append( alist[i-1] )
yield ret
data = { 'a': [1,2], 'b': [3,4,5], 'c': [1,4,7] }
pairs = list( kSubsets(data.keys(),2) ) + [ [k,k] for k in
data.iterkeys() ]
print pairs
for s in pairs:
for t in xcombine( data[s[0]], data[s[1]] ):
print "%s,'%s',%s,'%s'" % ( t[0], s[0], t[1], s[1] )
-------------------------------------------------------------------------
1,'a',1,'c'
1,'a',4,'c'
1,'a',7,'c'
2,'a',1,'c'
2,'a',4,'c'
2,'a',7,'c'
1,'a',3,'b'
1,'a',4,'b'
1,'a',5,'b'
2,'a',3,'b'
2,'a',4,'b'
2,'a',5,'b'
1,'c',3,'b'
1,'c',4,'b'
1,'c',5,'b'
4,'c',3,'b'
4,'c',4,'b'
4,'c',5,'b'
7,'c',3,'b'
7,'c',4,'b'
7,'c',5,'b'
1,'a',1,'a'
1,'a',2,'a'
2,'a',1,'a'
2,'a',2,'a'
1,'c',1,'c'
1,'c',4,'c'
1,'c',7,'c'
4,'c',1,'c'
4,'c',4,'c'
4,'c',7,'c'
7,'c',1,'c'
7,'c',4,'c'
7,'c',7,'c'
3,'b',3,'b'
3,'b',4,'b'
3,'b',5,'b'
4,'b',3,'b'
4,'b',4,'b'
4,'b',5,'b'
5,'b',3,'b'
5,'b',4,'b'
5,'b',5,'b'
1,'a',2,'b'
3,'a',5,'c'
3,'a',6,'c'
3,'a',7,'b'
8,'a',7,'b'
.
.
.
Now i need to generate 2 things by reading the file:
1) A dictionary with the numbers as keys and the letters as values.
e.g the above would give me a dictionary like
{1:'a', 2:'b', 3:'a', 5:'c', 6:'c' ........}
2) A list containing pairs of numbers from each line.
The above formmat would give me the list as
[[1,2],[3,5],[3,6][3,7][8,7]......]
I wrote the following codes for both of these but the problem is that
lines returns a list like ["1,'a',2,'b'","3,'a',5,'c","3,'a',6,'c'".....]
Now due to the "" around each line,it is treated like one object
and i cannot access the elements of a line.
[code]
#code to generate the dictionary
def get_colocations(filename):
lines = open(filename).read().split("\n")
colocnDict = {}
i = 0
for line in lines:
if i <= 2:
colocnDict[line[i]] = line[i+1]
i+=2
continue
return colocnDict
[/code]
[code]
def genPairs(filename):
lines = open(filename).read().split("\n")
pairList = []
for line in lines:
pair = [line[0],line[2]]
pairList.append(pair)
i+=2
continue
return pairList
[/code]
Please help :((
def get_dict( f ) :
out = {}
for line in file(f) :
n1,s1,n2,s2 = line.split(',')
out.update( { int(n1):s1[1], int(n2):s2[1] } )
return out
> 2) A list containing pairs of numbers from each line.
> The above formmat would give me the list as
> [[1,2],[3,5],[3,6][3,7][8,7]......]
def get_pairs( f ) :
out = []
for line in file(f) :
n1,_,n2,_ = line.split(',')
out.append( [int(n1),int(n2)] )
return out
Regards
Sreeram
Check out the csv module.
> .
> .
> .
> Now i need to generate 2 things by reading the file:
> 1) A dictionary with the numbers as keys and the letters as values.
> e.g the above would give me a dictionary like
> {1:'a', 2:'b', 3:'a', 5:'c', 6:'c' ........}
> 2) A list containing pairs of numbers from each line.
> The above formmat would give me the list as
> [[1,2],[3,5],[3,6][3,7][8,7]......]
>
> I wrote the following codes for both of these but the problem is that
> lines returns a list like ["1,'a',2,'b'","3,'a',5,'c","3,'a',6,'c'".....]
> Now due to the "" around each line,it is treated like one object
> and i cannot access the elements of a line.
You managed to split the file contents into lines using
lines = open(filename).read().split("\n")
Same principle applies to each line:
|>>> lines = ["1,'a',2,'b'","3,'a',5,'c","3,'a',6,'c'"]
|>>> lines[0].split(',')
['1', "'a'", '2', "'b'"]
|>>> lines[1].split(',')
['3', "'a'", '5', "'c"]
|>>>
>
> [code]
> #code to generate the dictionary
> def get_colocations(filename):
> lines = open(filename).read().split("\n")
> colocnDict = {}
> i = 0
> for line in lines:
> if i <= 2:
> colocnDict[line[i]] = line[i+1]
> i+=2
> continue
> return colocnDict
The return is indented too far; would return after 1st line.
> [/code]
>
> [code]
> def genPairs(filename):
> lines = open(filename).read().split("\n")
> pairList = []
> for line in lines:
> pair = [line[0],line[2]]
> pairList.append(pair)
> i+=2
i is not defined. This would cause an exception. Please *always* post
the code that you actually ran.
> continue
> return pairList
dedented too far!!
> [/code]
> Please help :((
def get_both(filename):
lines = open(filename).read().split("\n")
colocnDict = {}
pairList = []
for line in lines:
n1, b1, n2, b2 = line.split(",")
n1 = int(n1)
n2 = int(n2)
a1 = b1.strip("'")
a2 = b2.strip("'")
colocnDict[n1] = a1
colocnDict[n2] = a2
pairList.append([n1, n2])
return colocnDict, pairList
def get_both_csv(filename):
import csv
reader = csv.reader(open(filename, "rb"), quotechar="'")
colocnDict = {}
pairList = []
for n1, a1, n2, a2 in reader:
n1 = int(n1)
n2 = int(n2)
colocnDict[n1] = a1
colocnDict[n2] = a2
pairList.append([n1, n2])
return colocnDict, pairList
HTH,
John
>Thanks a lot Gerard and Roberto.but i think i should explain the exact
>thing with an example.
>Roberto what i have right now is concatenating the keys and the
>corresponding values:
>e.g {'a':[1,2],'b':[3,4,5],'c':[6,7]} should give me
>{'ab':[1,2][3,4,5] 'ac':[1,2][6,7] 'bc':[3,4,5][6,7]}
>The order doesnt matter here.It could be 'ac' followed by 'bc' and 'ac'.
>Also order doesnt matter in a string:the pair 'ab':[1,2][3,4,5] is same as
>'ba':[3,4,5][1,2].
>This representation means 'a' corresponds to the list [1,2] and 'b'
>corresponds to the list [3,4,5].
>Now, for each key-value pair,e.g for 'ab' i must check each feature in the
>list of 'a' i.e. [1,2] with each feature in list of 'b' i.e. [3,4,5].So I
>want to take cartesian product of ONLY the 2 lists [1,2] and [3,4,5].
>Finally i want to check each pair if it is present in the file,whose
>format i had specified.
>The code Gerard has specified takes cartesian products of every 2 lists.
Hi Garish,
it's better to reply to the Group.
>Now, for each key-value pair,e.g for 'ab' i must check each feature in the
>list of 'a' i.e. [1,2] with each feature in list of 'b' i.e. [3,4,5].So I
>want to take cartesian product of ONLY the 2 lists [1,2] and [3,4,5].
I'm confused. You say *for each* key-value pair, and you wrote above
that the keys were the 'concatenation' of "every 2 keys of a
dictionary".
Sorry, too early for me. Maybe if you list every case you want, given
the example data.
All the best.
Gerard
And error i get in your code is:
for n1, a1, n2, a2 in reader:
ValueError: need more than 0 values to unpack
Any ideas why this is happening?
Thanks a lot,
girish
In the case of my code, this is consistent with the line being empty,
probably the last line. As my mentor Bruno D. would say, your test data
does not match your spec :-) Which do you want to change, the spec or
the data?
You can change my csv-reading code to detect dodgy data like this (for
example):
for row in reader:
if not row:
continue # ignore empty lines, wherever they appear
if len(row) != 4:
raise ValueError("Malformed row %r" % row)
n1, a1, n2, a2 = row
In the case of Sreeram's code, perhaps you could try inserting
print "line = ", repr(line)
before the statement that is causing the error.
>
> Thanks a lot,
> girish
>
>
>
Running this:
open("some.text.file", "w").write("""\
1,'a',2,'b'
3,'a',5,'c'
3,'a',6,'c'
3,'a',7,'b'
8,'a',7,'b'
""")
import csv
class dialect(csv.excel):
quotechar = "'"
reader = csv.reader(open("some.text.file", "rb"), dialect=dialect)
mydict = {}
mylist = []
for row in reader:
numbers = [int(n) for n in row[::2]]
letters = row[1::2]
mydict.update(dict(zip(numbers, letters)))
mylist.append(numbers)
print mydict
print mylist
import os
os.unlink("some.text.file")
displays this:
{1: 'a', 2: 'b', 3: 'a', 5: 'c', 6: 'c', 7: 'b', 8: 'a'}
[[1, 2], [3, 5], [3, 6], [3, 7], [8, 7]]
That seems to be approximately what you're looking for.
Skip
The problem if that the two lists aren't distinguishable when
concatenated, so what you get is [1, 2, 3, 4, 5]. You have to pack
both lists in a tuple: {'ab': ([1, 2], [3, 4, 5]), ...}
>>> d = {'a':[1, 2], 'b':[3, 4, 5], 'c':[6, 7]}
>>> d2 = dict(((i + j), (d[i], d[j])) for i in d for j in d if i < j)
>>> d2
{'ac': ([1, 2], [6, 7]), 'ab': ([1, 2], [3, 4, 5]), 'bc': ([3, 4, 5], [6, 7])}
> >Now, for each key-value pair,e.g for 'ab' i must check each feature in the
> >list of 'a' i.e. [1,2] with each feature in list of 'b' i.e. [3,4,5].So I
> >want to take cartesian product of ONLY the 2 lists [1,2] and [3,4,5].
You can do this without creating an additional dictionary:
>>> d = {'a':[1, 2], 'b':[3, 4, 5], 'c':[6, 7]}
>>> pairs = [i + j for i in d for j in d if i < j]
>>> for i, j in pairs:
... cartesian_product = [(x, y) for x in d[i] for y in d[j]]
... print i + j, cartesian_product
...
ac [(1, 6), (1, 7), (2, 6), (2, 7)]
ab [(1, 3), (1, 4), (1, 5), (2, 3), (2, 4), (2, 5)]
bc [(3, 6), (3, 7), (4, 6), (4, 7), (5, 6), (5, 7)]
You can do whatever you want with this cartesian product inside the loop.
> >Finally i want to check each pair if it is present in the file,whose
> >format i had specified.
I don't understand the semantics of the file format, so I leave this
as an exercise to the reader :)
Best regards.
--
Roberto Bonvallet