I was learning about regularization and came across the term called regularization parameter.

I see that it is called lambda in theory but when I looked at the python implementation, I see that it is denoted as alpha. Here is the link1 and link2

Am I right to understand that both mean the same?

Is there any difference between regularization paramter lambda and regularization parameter alpha ?


1 Answer 1


No difference. It's just a symbol. Sometimes mathematics uses symbols by convention, but there's no rule or requirement that you must use a certain symbol for a concept.

In this particular case, the word lambda is reserved by the Python language, so alpha avoids overlapping with that word.

As an aside, one sharp corner in sklearn is that sklearn.linear_model.LogisticRegression uses the inverse of regularization strength as the regularization parameter, so $C=\lambda^{-1}$. In a different package, you might set $\lambda=10$, but for this class, you would get an equivalent result with $C=0.1$.


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