sorting - python sort list of lists with casting -

i know tat similar questions has been asked several times. , how use search function, still not work.

so here problem setup. have list of lists containing strings. 1 column contains strings represent float values. , column want sort by. problem is, python seems ignore - (minus) sign on entries. example list of:

[[blaa, '0.3', bli], [bla, '0.1', blub], [bla, '-0.2', blub]] 

gets sorted this:

[[bla, '0.1', blub], [bla, '-0.2', blub], [blaa, '0.3', bli]] 

and not how should be:

[[bla, '-0.2', blub],[bla, '0.1', blub], [blaa, '0.3', bli]] 

so far have tried:

• casting second column float , sorting column

like:

for in mylist:   i[1] = float(i[1])      mylist.sort(key=lambda x: x[1]) 

or with

for in mylist:   i[1] = float(i[1])   mylist.sort(key=operator.itemgetter(1)) 

• i tried define own compare function:

like:

mylist.sort(cmp=lambda x,y: cmp(float(x), float(y)), key=operator.itemgetter(1)) 

and other combination of above methods, same sorted. far no success, minus sign gets ignored every time. how solve this?

[edit] tried ignacio suggestion. should mention have use python 2.5 .

l = [["blaa", "0.3", "bli"], ["bla", "0.1", "blub"], ["bla", "-0.2", "blub"]]  l.sort(key=lambda x: float(x[1]))  >>> [['bla', '-0.2', 'blub'], ['bla', '0.1', 'blub'], ['blaa', '0.3', 'bli']]