dictionary of list from a file

[Paul McGuire]

<andrea.spitaleri at gmail.com> wrote in message 
news:1159967361.355323.201050 at m7g2000cwm.googlegroups.com...
> Hi guys,
> this is my first post. my "programming" background is perlish scripting
> and now I am learning python. I need to create a dictionary of list
> from a file. Normally in perl I use to do like:
>
> while(<IN>){
>          @info=split(/ +/,$_);
>          push (@{$tmp{$info[0]}},$info[1]);
> }
>
> and then
> foreach $key (keys %tmp){
>           print "$key -> @{$tmp{$key}}\n";
> }
> i get
>
> 2 -> 1  2 3 4
> 7 -> 7 8 9 10
>
> in python I tried:
> b={}
> a=[]
> for line in fl.readlines():
>         info=lines.split()
>         b[info[0]] = a.append(info[1])
>
> and then
> for i in b:
>     print i,b[i]
> i get
> 2 None
> 7 None
>
> data file is:
> 2 1
> 2 2
> 2 3
> 2 4
> 7 7
> 7 8
> 7 9
> 7 10
>
> Any help??
> Thanks in advance
> Best Regards
>
> Andrea
>

I'll see your perlish line noise, and raise you this obfuscapython:  :)

data = """\
2 1  2 3 4
  7 7 8 9 10
5 1 3 5 7 9
2 6 8 10""".split('\n')  # similar to file.readlines(), but easier to paste 
into news post
import operator, itertools
item = operator.itemgetter
b = dict( (k,sum(map(lambda g:g[1:],grps),[]))
             for (k,grps) in itertools.groupby( sorted( 
map(str.split,data) ), item(0) ) )
for item in sorted(b.items()):
    print "%s -> %s" % item

prints:
2 -> ['1', '2', '3', '4', '6', '8', '10']
5 -> ['1', '3', '5', '7', '9']
7 -> ['7', '8', '9', '10']

-- Paul