Y_train values for symbolicRegressor
Sorry for the late replay. gplearn supports regression (numeric y) with the SymbolicRegressor estimator, and with the newly released gplearn 0.4.0 we also support binary classification (two labels in y) using the SymbolicClassifier. From the sounds of things though, you have a multi-label problem which gplearn does not currently support. It may be something we look to support in the future.
I split my dataset in X_train, Y_train, X_test and Y_test, and then I used the symbolicRegressor...
I've already convert the string values from Dataframe in float values.
But by applying the symbolicRegressor I get this error: 

ValueError: could not convert string to float: 'd'

Where 'd' is a value from Y.
Since all my values in Y_train and Y_test are alphabetic character because they are the "labels", I can not understand why the symbolicRegressor tries to get a float number ..
Any idea?