Variance threshold with python problem
0.8 is the threshold value meaning you want to exclude columns(features) with at least 80% of values is 0 or 1: sort of unbalanced dummies. This is only applied well to dummies, but not necessarily general numerical values.
For numerical, you can test RFECV function in feature_selection package from sciki-learn, the syntax as follows:

feature_folds = ms.KFold(n_splits=10, shuffle = True) # cross-validation folds

selector = fs.RFECV(estimator = your_model, cv = feature_folds,
                      scoring = 'roc_auc') 

selector = selector.fit(your_features, your_labels)

selector.support_