dictionary of list from a file

[andrea.spitaleri at gmail.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