You can do it by first searching one minimum value and then look for another ones based by the minimum value found.
listo = [('a','1'),('b','0'),('c','2'),('d','0')]
minValue = min(listo, key=lambda x: x[1])[1]
minValueList = [x for x in listo if x[1] == minValue]
Another approach could be making your own minimum function that uses some kind of list of minimum values but probably it would be much slower for bigger problems.