When to consider a target Variable unbalanced?
There's not a strict threshold about what ratio is considered as unbalanced. But in general, 30 percent is not usually a sign of unbalanced classification.

You can although try different methods for checking if your classification method is accurate and predicts correctly or not, like resampling, over-sampling, under-sampling


increasing the number of records (samples) in the class with less frequency.
randomly removing the samples from the class with higher frequency.


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from sklearn.utils import resample