sklearn/datasets/tests/data/svmlight_classification.txt

# comment
# note: the next line contains a tab
1.0 3:2.5 	   11:-5.2 16:1.5 # and an inline comment
2.0 6:1.0 13:-3 
# another comment
3.0 21:27
4.0 2:1.234567890123456e10 # double precision value
1.0     # empty line, all zeros
2.0 3:0 # explicit zeros