Classifier that outputs most probable classes with their class probabilities?

Hi,

does anyone a classifier that does not just output one assigned class for 
each data item,
but rather a set of classes with their class probabilities?

Example: Text1 is {sports: 75%, news: 25%}, Text2 is {entertainment: 80%, 
modern-life: 20%}
Meaning: Text1 belongs most likely to the class "sports texts",
          but there is a 25% probability that it instead belongs to "news 
texts".
          Text2 respectively.

A ready-to-use software package would be nice. Or a package where it would 
be easy to add in the source code.

Thanks for every hint!
Andi

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