take a look at the documentations (http://scikit-learn.org/stable/modules/generated/sklearn.linear_model.LogisticRegression.html), offset coefficient isn’t stored by lr.coef_
coef_ array, shape = [n_classes-1, n_features] Coefficient of the
features in the decision function. coef_ is readonly property derived
from raw_coef_ that follows the internal memory layout of liblinear.
intercept_ array, shape = [n_classes-1] Intercept (a.k.a. bias) added
to the decision function. It is available only when parameter
intercept is set to True.
try:
sigmoid( dot([val1, val2], lr.coef_) + lr.intercept_ )