basic.py

"""Wrapper c_api of LightGBM"""
from __future__ import absolute_import

import sys
import os
import ctypes
import collections
import re
import tempfile

import numpy as np
import scipy.sparse

from .libpath import find_lib_path

IS_PY3 = (sys.version_info[0] == 3)

def _load_lib():
    """Load LightGBM Library."""
    lib_path = find_lib_path()
    if len(lib_path) == 0:
        return None
    lib = ctypes.cdll.LoadLibrary(lib_path[0])
    lib.LGBM_GetLastError.restype = ctypes.c_char_p
    return lib

_LIB = _load_lib()

class LightGBMError(Exception):
    """Error throwed by LightGBM"""
    pass

def _safe_call(ret):
    """Check the return value of C API call
    Parameters
    ----------
    ret : int
        return value from API calls
    """
    if ret != 0:
        raise LightGBMError(_LIB.LGBM_GetLastError())

def is_str(s):
    if IS_PY3:
        return isinstance(s, str)
    else:
        return isinstance(s, basestring)

def is_numpy_object(data):
    return type(data).__module__ == np.__name__

def is_numpy_1d_array(data):
    if isinstance(data, np.ndarray) and len(data.shape) == 1:
        return True
    else:
        return False

def is_1d_list(data):
    if not isinstance(data, list):
        return False
    if len(data) > 0:
        if not isinstance(data[0], (int, float, bool) ):
            return False
    return True

def list_to_1d_numpy(data, dtype):
    if is_numpy_1d_array(data):
        if data.dtype == dtype:
            return data
        else:
            return data.astype(dtype=dtype, copy=False)
    elif is_1d_list(data):
        return np.array(data, dtype=dtype, copy=False)
    else:
        raise TypeError("Unknow type({})".format(type(data).__name__))

def cfloat32_array_to_numpy(cptr, length):
    """Convert a ctypes float pointer array to a numpy array.
    """
    if isinstance(cptr, ctypes.POINTER(ctypes.c_float)):
        res = np.fromiter(cptr, dtype=np.float32, count=length)
        return res
    else:
        raise RuntimeError('expected float pointer')

def cint32_array_to_numpy(cptr, length):
    """Convert a ctypes float pointer array to a numpy array.
    """
    if isinstance(cptr, ctypes.POINTER(ctypes.c_int32)):
        res = np.fromiter(cptr, dtype=np.int32, count=length)
        return res
    else:
        raise RuntimeError('expected int pointer')

def c_str(string):
    """Convert a python string to cstring."""
    return ctypes.c_char_p(string.encode('utf-8'))

def c_array(ctype, values):
    """Convert a python array to c array."""
    return (ctype * len(values))(*values)

def param_dict_to_str(data):
    if data is None or len(data) == 0:
        return ""
    pairs = []
    for key, val in data.items():
        if is_str(val):
            pairs.append(str(key)+'='+str(val))
        elif isinstance(val, (list, tuple)):
            pairs.append(str(key)+'='+','.join(map(str,val)))
        elif isinstance(val, (int, float, bool)):
            pairs.append(str(key)+'='+str(val))
        else:
            raise TypeError('unknow type of parameter:%s , got:%s' %(key, type(val).__name__))
    return ' '.join(pairs)
"""marco definition of data type in c_api of LightGBM"""
C_API_DTYPE_FLOAT32 =0
C_API_DTYPE_FLOAT64 =1
C_API_DTYPE_INT32   =2
C_API_DTYPE_INT64   =3
"""Matric is row major in python"""
C_API_IS_ROW_MAJOR  =1

C_API_PREDICT_NORMAL     =0
C_API_PREDICT_RAW_SCORE  =1
C_API_PREDICT_LEAF_INDEX =2

FIELD_TYPE_MAPPER = {"label":C_API_DTYPE_FLOAT32, 
"wegiht":C_API_DTYPE_FLOAT32, 
"init_score":C_API_DTYPE_FLOAT32,
"group":C_API_DTYPE_INT32,
 }

def c_float_array(data):
    """Convert numpy array / list to c float array."""
    if is_1d_list(data):
        data = np.array(data, copy=False)
    if is_numpy_1d_array(data):
        if data.dtype == np.float32:
            ptr_data = data.ctypes.data_as(ctypes.POINTER(ctypes.c_float))
            type_data = C_API_DTYPE_FLOAT32
        elif data.dtype == np.float64:
            ptr_data = data.ctypes.data_as(ctypes.POINTER(ctypes.c_double))
            type_data = C_API_DTYPE_FLOAT64
        else:
            raise TypeError("expected np.float32 or np.float64, met type({})".format(data.dtype))
    else:
        raise TypeError("Unknow type({})".format(type(data).__name__))
    return (ptr_data, type_data)

def c_int_array(data):
    """Convert numpy array to c int array."""
    if is_1d_list(data):
        data = np.array(data, copy=False)
    if is_numpy_1d_array(data):
        if data.dtype == np.int32:
            ptr_data = data.ctypes.data_as(ctypes.POINTER(ctypes.c_int32))
            type_data = C_API_DTYPE_INT32
        elif data.dtype == np.int64:
            ptr_data = data.ctypes.data_as(ctypes.POINTER(ctypes.c_int64))
            type_data = C_API_DTYPE_INT64
        else:
            raise TypeError("expected np.int32 or np.int64, met type({})".format(data.dtype))
    else:
        raise TypeError("Unknow type({})".format(type(data).__name__))
    return (ptr_data, type_data)

class Predictor(object):
    """"A Predictor of LightGBM.
    """
    def __init__(self,model_file=None, booster_handle=None, is_manage_handle=True):
        """Initialize the Predictor.

        Parameters
        ----------
        model_file : string
            Path to the model file. 
        """
        self.handle = ctypes.c_void_p()
        self.__is_manage_handle = True
        if model_file is not None:
            """Prediction task"""
            out_num_iterations = ctypes.c_int64(0)
            _safe_call(_LIB.LGBM_BoosterCreateFromModelfile(
                c_str(model_file), 
                ctypes.byref(out_num_iterations),
                ctypes.byref(self.handle)))
            out_num_class = ctypes.c_int64(0)
            _safe_call(_LIB.LGBM_BoosterGetNumClasses(
                self.handle,
                ctypes.byref(out_num_class)))
            self.num_class = out_num_class.value
            self.__num_total_iteration = out_num_iterations.value 
        elif booster_handle is not None:
            self.__is_manage_handle = is_manage_handle
            self.handle = booster_handle
            out_num_class = ctypes.c_int64(0)
            _safe_call(_LIB.LGBM_BoosterGetNumClasses(
                self.handle,
                ctypes.byref(out_num_class)))
            self.num_class = out_num_class.value
            out_num_iterations = ctypes.c_int64(0)
            _safe_call(_LIB.LGBM_BoosterGetCurrentIteration(
                self.handle,
                ctypes.byref(out_num_iterations)))
            self.__num_total_iteration = out_num_iterations.value 
        else:
            raise TypeError('Need Model file to create a booster')

    def __del__(self):
        if self.__is_manage_handle:
            _safe_call(_LIB.LGBM_BoosterFree(self.handle))


    def predict(self, data, num_iteration=-1, raw_score=False, pred_leaf=False, data_has_header=False, is_reshape=True):
        """
        Predict logic

        Parameters
        ----------
        data : string/numpy array/scipy.sparse
            Data source for prediction
            When data is string type, it represents the path of txt file,
        num_iteration : 
            used iteration for prediction
        raw_score : bool 
            True for predict raw score
        pred_leaf : bool
            True for predict leaf index
        data_has_header : bool
            Used for txt data
        is_reshape : bool
            True for reshape to [nrow, ...] 

        Returns
        -------
        Prediction result
        """
        if isinstance(data, Dataset):
            raise TypeError("cannot use Dataset instance for prediction, please use raw data instead")
        predict_type = C_API_PREDICT_NORMAL
        if raw_score:
            predict_type = C_API_PREDICT_RAW_SCORE
        if pred_leaf:
            predict_type = C_API_PREDICT_LEAF_INDEX
        int_data_has_header = 1 if data_has_header else 0
        if num_iteration > self.__num_total_iteration:
            num_iteration = self.__num_total_iteration
        if is_str(data):
            tmp_pred_fname = tempfile.NamedTemporaryFile(prefix="lightgbm_tmp_pred_").name
            _safe_call(_LIB.LGBM_BoosterPredictForFile(
                self.handle,
                c_str(data), 
                int_data_has_header,
                predict_type,
                num_iteration,
                c_str(tmp_pred_fname)))
            tmp_file = open(tmp_pred_fname,"r")
            lines = tmp_file.readlines()
            tmp_file.close()
            nrow = len(lines)
            preds = []
            for line in lines:
                for token in line.split('\t'):
                    preds.append(float(token))
            preds = np.array(preds, copy=False)
            os.remove(tmp_pred_fname)
        elif isinstance(data, scipy.sparse.csr_matrix):
            preds, nrow = self.__pred_for_csr(data, num_iteration, predict_type)
        elif isinstance(data, np.ndarray):
            preds, nrow = self.__pred_for_np2d(data, num_iteration, predict_type)
        else:
            try:
                csr = scipy.sparse.csr_matrix(data)
                preds, nrow = self.__pred_for_csr(csr, num_iteration, predict_type)
            except:
                raise TypeError('can not predict data for type {}'.format(type(data).__name__))
        if pred_leaf:
            preds = preds.astype(np.int32)
        if preds.size != nrow and is_reshape:
            if preds.size % nrow == 0:
                ncol = int(preds.size / nrow)
                preds = preds.reshape(nrow, ncol)
            else:
                raise ValueError('len of predict result(%d) cannot be divide nrow(%d)' %(preds.size, nrow) )
        return preds

    def __get_num_preds(self, num_iteration, nrow, predict_type):
        n_preds = self.num_class * nrow
        if predict_type == C_API_PREDICT_LEAF_INDEX:
            if num_iteration > 0:
                n_preds *= min(num_iteration, self.__num_total_iteration)
            else:
                n_preds *= self.__num_total_iteration
        return n_preds

    def __pred_for_np2d(self, mat, num_iteration, predict_type):
        """
        Predict for a 2-D numpy matrix.
        """
        if len(mat.shape) != 2:
            raise ValueError('Input numpy.ndarray must be 2 dimensional')

        if mat.dtype == np.float32 or mat.dtype == np.float64:
            data = np.array(mat.reshape(mat.size), dtype=mat.dtype, copy=False)
        else:
            """change non-float data to float data, need to copy"""
            data = np.array(mat.reshape(mat.size), dtype=np.float32)
        ptr_data, type_ptr_data = c_float_array(data)
        n_preds = self.__get_num_preds(num_iteration, mat.shape[0], predict_type)
        preds = np.zeros(n_preds, dtype=np.float32)
        out_num_preds = ctypes.c_int64(0)
        _safe_call(_LIB.LGBM_BoosterPredictForMat(
            self.handle,
            ptr_data, 
            type_ptr_data,
            mat.shape[0],
            mat.shape[1],
            C_API_IS_ROW_MAJOR,
            predict_type,
            num_iteration,
            ctypes.byref(out_num_preds),
            preds.ctypes.data_as(ctypes.POINTER(ctypes.c_float))
            ))
        if n_preds != out_num_preds.value:
            raise ValueError("incorrect number for predict result")
        return preds, mat.shape[0]

    def __pred_for_csr(self, csr, num_iteration, predict_type):
        """
        Predict for a csr data
        """
        nrow = len(csr.indptr) - 1
        n_preds = self.__get_num_preds(num_iteration, nrow, predict_type)
        preds = np.zeros(n_preds, dtype=np.float32)
        out_num_preds = ctypes.c_int64(0)

        ptr_indptr, type_ptr_indptr = c_int_array(csr.indptr)
        ptr_data, type_ptr_data = c_float_array(csr.data)

        _safe_call(_LIB.LGBM_BoosterPredictForCSR(
            self.handle,
            ptr_indptr, 
            type_ptr_indptr,
            csr.indices.ctypes.data_as(ctypes.POINTER(ctypes.c_int32)),
            ptr_data,
            type_ptr_data, 
            len(csr.indptr), 
            len(csr.data),
            csr.shape[1], 
            predict_type,
            num_iteration,
            ctypes.byref(out_num_preds),
            preds.ctypes.data_as(ctypes.POINTER(ctypes.c_float))
            ))
        if n_preds != out_num_preds.value:
            raise ValueError("incorrect number for predict result")
        return preds, nrow


class Dataset(object):
    """Dataset used in LightGBM.

    Dataset is a internal data structure that used by LightGBM
    """

    def __init__(self, data, label=None, max_bin=255, reference=None,
        weight=None, group=None, predictor=None,
        silent=False, params=None):
        """
        Dataset used in LightGBM.

        Parameters
        ----------
        data : string/numpy array/scipy.sparse
            Data source of Dataset.
            When data is string type, it represents the path of txt file,
        label : list or numpy 1-D array, optional
            Label of the data
        max_bin : int, required
            max number of discrete bin for features 
        reference : Other Dataset, optional
            If this dataset validation, need to use training data as reference
        weight : list or numpy 1-D array , optional
            Weight for each instance.
        group : list or numpy 1-D array , optional
            group/query size for dataset
        silent : boolean, optional
            Whether print messages during construction
        params: dict, optional
            other parameters
        """
        self.__label = None
        self.__weight = None
        self.__init_score = None
        self.__group = None
        if data is None:
            self.handle = None
            return
        self.data_has_header = False
        """process for args"""
        params = {} if params is None else params
        self.max_bin = max_bin
        self.predictor = predictor
        params["max_bin"] = max_bin
        if silent:
            params["verbose"] = 0
        elif "verbose" not in params:
            params["verbose"] = 1
        params_str = param_dict_to_str(params)
        """process for reference dataset"""
        ref_dataset = None
        if isinstance(reference, Dataset):
            ref_dataset = ctypes.byref(reference.handle)
        elif reference is not None:
            raise TypeError('Reference dataset should be None or dataset instance')
        """start construct data"""
        if is_str(data):
            """check data has header or not"""
            if "has_header" in params or "header" in params:
                if params["has_header"].lower() == "true" or params["header"].lower() == "true":
                    self.data_has_header = True
            self.handle = ctypes.c_void_p()
            _safe_call(_LIB.LGBM_DatasetCreateFromFile(
                c_str(data), 
                c_str(params_str), 
                ref_dataset,
                ctypes.byref(self.handle)))
        elif isinstance(data, scipy.sparse.csr_matrix):
            self.__init_from_csr(data, params_str, ref_dataset)
        elif isinstance(data, np.ndarray):
            self.__init_from_np2d(data, params_str, ref_dataset)
        else:
            try:
                csr = scipy.sparse.csr_matrix(data)
                self.__init_from_csr(csr, params_str, ref_dataset)
            except:
                raise TypeError('can not initialize Dataset from {}'.format(type(data).__name__))
        if label is not None:
            self.set_label(label)
        if self.get_label() is None:
            raise ValueError("label should not be None")
        if weight is not None:
            self.set_weight(weight)
        if group is not None:
            self.set_group(group)
        # load init score
        if self.predictor is not None and isinstance(self.predictor, Predictor):
            init_score = self.predictor.predict(data, 
                raw_score=True, 
                data_has_header=self.data_has_header, 
                is_reshape=False)
            if self.predictor.num_class > 1:
                # need re group init score
                new_init_score = np.zeros(init_score.size(), dtype=np.float32)
                num_data = self.num_data()
                for i in range(num_data):
                    for j in range(self.predictor.num_class):
                        new_init_score[j * num_data + i] = init_score[i * self.predictor.num_class + j]
                init_score = new_init_score
            self.set_init_score(init_score)

    def create_valid(self, data, label=None, weight=None, group=None, 
        silent=False, params=None):
        """
        Create validation data align with current dataset

        Parameters
        ----------
        data : string/numpy array/scipy.sparse
            Data source of Dataset.
            When data is string type, it represents the path of txt file,
        label : list or numpy 1-D array, optional
            Label of the training data.
        weight : list or numpy 1-D array , optional
            Weight for each instance.
        group : list or numpy 1-D array , optional
            group/query size for dataset
        silent : boolean, optional
            Whether print messages during construction
        params: dict, optional
            other parameters
        """
        return Dataset(data, label=label, max_bin=self.max_bin, reference=self,
            weight=weight, group=group, predictor=self.predictor, 
            silent=silent, params=params)

    def subset(self, used_indices, params=None):
        """
        Get subset of current dataset
        """
        used_indices = list_to_1d_numpy(used_indices, np.int32)
        ret = Dataset(None)
        ret.handle = ctypes.c_void_p()
        params_str = param_dict_to_str(params)
        _safe_call(_LIB.LGBM_DatasetGetSubset(
            ctypes.byref(self.handle), 
            used_indices.ctypes.data_as(ctypes.POINTER(ctypes.c_int32)),
            used_indices.shape[0],
            c_str(params_str), 
            ctypes.byref(ret.handle)))
        ret.max_bin = self.max_bin
        ret.predictor = self.predictor
        if ret.get_label() is None:
            raise ValueError("label should not be None")
        return ret

    def __init_from_np2d(self, mat, params_str, ref_dataset):
        """
        Initialize data from a 2-D numpy matrix.
        """
        if len(mat.shape) != 2:
            raise ValueError('Input numpy.ndarray must be 2 dimensional')

        self.handle = ctypes.c_void_p()
        if mat.dtype == np.float32 or mat.dtype == np.float64:
            data = np.array(mat.reshape(mat.size), dtype=mat.dtype, copy=False)
        else:
            """change non-float data to float data, need to copy"""
            data = np.array(mat.reshape(mat.size), dtype=np.float32)

        ptr_data, type_ptr_data = c_float_array(data)
        _safe_call(_LIB.LGBM_DatasetCreateFromMat(
            ptr_data, 
            type_ptr_data,
            mat.shape[0],
            mat.shape[1],
            C_API_IS_ROW_MAJOR,
            c_str(params_str), 
            ref_dataset, 
            ctypes.byref(self.handle)))

    def __init_from_csr(self, csr, params_str, ref_dataset):
        """
        Initialize data from a CSR matrix.
        """
        if len(csr.indices) != len(csr.data):
            raise ValueError('length mismatch: {} vs {}'.format(len(csr.indices), len(csr.data)))
        self.handle = ctypes.c_void_p()

        ptr_indptr, type_ptr_indptr = c_int_array(csr.indptr)
        ptr_data, type_ptr_data = c_float_array(csr.data)

        _safe_call(_LIB.LGBM_DatasetCreateFromCSR(
            ptr_indptr, 
            type_ptr_indptr,
            csr.indices.ctypes.data_as(ctypes.POINTER(ctypes.c_int32)),
            ptr_data,
            type_ptr_data, 
            len(csr.indptr), 
            len(csr.data),
            csr.shape[1], 
            c_str(params_str), 
            ref_dataset, 
            ctypes.byref(self.handle)))

    def __del__(self):
        _safe_call(_LIB.LGBM_DatasetFree(self.handle))

    def get_field(self, field_name):
        """Get property from the Dataset.

        Parameters
        ----------
        field_name: str
            The field name of the information

        Returns
        -------
        info : array
            a numpy array of information of the data
        """
        tmp_out_len = ctypes.c_int64()
        out_type = ctypes.c_int32()
        ret = ctypes.POINTER(ctypes.c_void_p)()
        _safe_call(_LIB.LGBM_DatasetGetField(
            self.handle,
            c_str(field_name),
            ctypes.byref(tmp_out_len),
            ctypes.byref(ret),
            ctypes.byref(out_type)))
        if out_type.value != FIELD_TYPE_MAPPER[field_name]:
            raise TypeError("Return type error for get_field")
        if tmp_out_len.value == 0:
            return None
        if out_type.value == C_API_DTYPE_INT32:
            return cint32_array_to_numpy(ctypes.cast(ret, ctypes.POINTER(ctypes.c_int32)), tmp_out_len.value)
        elif out_type.value == C_API_DTYPE_FLOAT32:
            return cfloat32_array_to_numpy(ctypes.cast(ret, ctypes.POINTER(ctypes.c_float)), tmp_out_len.value)
        else:
            raise TypeError("unknow type")

    def set_field(self, field_name, data):
        """Set property into the Dataset.

        Parameters
        ----------
        field_name: str
            The field name of the information

        data: numpy array or list or None
            The array ofdata to be set
        """
        if data is None:
            """set to None"""
            _safe_call(_LIB.LGBM_DatasetSetField(
                self.handle,
                c_str(field_name),
                None,
                0,
                FIELD_TYPE_MAPPER[field_name]))
            return
        if not is_numpy_1d_array(data):
            raise TypeError("Unknow type({})".format(type(data).__name__))
        if data.dtype == np.float32:
            ptr_data = data.ctypes.data_as(ctypes.POINTER(ctypes.c_float))
            type_data = C_API_DTYPE_FLOAT32
        elif data.dtype == np.int32:
            ptr_data = data.ctypes.data_as(ctypes.POINTER(ctypes.c_int32))
            type_data = C_API_DTYPE_INT32
        else:
            raise TypeError("excepted np.float32 or np.int32, met type({})".format(data.dtype))
        if type_data != FIELD_TYPE_MAPPER[field_name]:
            raise TypeError("type error for set_field")
        _safe_call(_LIB.LGBM_DatasetSetField(
            self.handle,
            c_str(field_name),
            ptr_data,
            len(data),
            type_data))


    def save_binary(self, filename):
        """Save Dataset to binary file

        Parameters
        ----------
        filename : string
            Name of the output file.
        """
        _safe_call(_LIB.LGBM_DatasetSaveBinary(
            self.handle,
            c_str(filename)))

    def set_label(self, label):
        """Set label of Dataset

        Parameters
        ----------
        label: array like
            The label information to be set into Dataset
        """
        label = list_to_1d_numpy(label, np.float32)
        self.__label = label
        self.set_field('label', label)

    def set_weight(self, weight):
        """ Set weight of each instance.

        Parameters
        ----------
        weight : array like
            Weight for each data point
        """
        if weight is not None:
            weight = list_to_1d_numpy(weight, np.float32)
        self.__weight = weight
        self.set_field('weight', weight)

    def set_init_score(self, score):
        """ Set init score of booster to start from.
        Parameters
        ----------
        score: array like

        """
        if score is not None:
            score = list_to_1d_numpy(score, np.float32)
        self.__init_score = score
        self.set_field('init_score', score)

    def set_group(self, group):
        """Set group size of Dataset (used for ranking).

        Parameters
        ----------
        group : array like
            Group size of each group
        """
        if group is not None:
            group = list_to_1d_numpy(group, np.int32)
        self.__group = group
        self.set_field('group', group)


    def get_label(self):
        """Get the label of the Dataset.

        Returns
        -------
        label : array
        """
        if self.__label is None:
            self.__label = self.get_field('label')
        if self.__label is None:
            raise TypeError("label should not be None")
        return self.__label

    def get_weight(self):
        """Get the weight of the Dataset.

        Returns
        -------
        weight : array
        """
        if self.__weight is None:
            self.__weight = self.get_field('weight')
        return self.__weight

    def get_init_score(self):
        """Get the initial score of the Dataset.

        Returns
        -------
        init_score : array
        """
        if self.__init_score is None:
            self.__init_score = self.get_field('init_score')
        return self.__init_score

    def get_group(self):
        """Get the initial score of the Dataset.

        Returns
        -------
        init_score : array
        """
        if self.__group is None:
            self.__group = self.get_field('group')
        return self.__group

    def num_data(self):
        """Get the number of rows in the Dataset.

        Returns
        -------
        number of rows : int
        """
        ret = ctypes.c_int64()
        _safe_call(_LIB.LGBM_DatasetGetNumData(self.handle,
                                         ctypes.byref(ret)))
        return ret.value

    def num_feature(self):
        """Get the number of columns (features) in the Dataset.

        Returns
        -------
        number of columns : int
        """
        ret = ctypes.c_int64()
        _safe_call(_LIB.LGBM_DatasetGetNumFeature(self.handle,
                                         ctypes.byref(ret)))
        return ret.value

class Booster(object):
    """"A Booster of of LightGBM.
    """
    def __init__(self, params=None, train_set=None, model_file=None, silent=False):
        """Initialize the Booster.

        Parameters
        ----------
        params : dict
            Parameters for boosters.
        train_set : Dataset
            training dataset
        model_file : string
            Path to the model file. 
        silent : boolean, optional
            Whether print messages during construction
        """
        self.handle = ctypes.c_void_p()
        self.__need_reload_eval_info = True
        self.__is_manage_handle = True
        self.__train_data_name = "training"
        self.__attr = {}
        params = {} if params is None else params
        if silent:
            params["verbose"] = 0
        elif "verbose" not in params:
            params["verbose"] = 1
        if train_set is not None:
            """Training task"""
            if not isinstance(train_set, Dataset):
                raise TypeError('training data should be Dataset instance, met{}'.format(type(train_set).__name__))
            params_str = param_dict_to_str(params)
            """construct booster object"""
            _safe_call(_LIB.LGBM_BoosterCreate(
                train_set.handle, 
                c_str(params_str),
                ctypes.byref(self.handle)))
            """save reference to data"""
            self.train_set = train_set
            self.valid_sets = []
            self.name_valid_sets = []
            self.__num_dataset = 1
            self.init_predictor = train_set.predictor
            if self.init_predictor is not None:
                _safe_call(_LIB.LGBM_BoosterMerge(
                    self.handle,
                    self.init_predictor.handle))
            out_num_class = ctypes.c_int64(0)
            _safe_call(_LIB.LGBM_BoosterGetNumClasses(
                self.handle,
                ctypes.byref(out_num_class)))
            self.__num_class = out_num_class.value
            """buffer for inner predict"""
            self.__inner_predict_buffer = [None]
            self.__is_predicted_cur_iter = [False]
            self.__get_eval_info()
        elif model_file is not None:
            """Prediction task"""
            out_num_iterations = ctypes.c_int64(0)
            _safe_call(_LIB.LGBM_BoosterCreateFromModelfile(
                c_str(model_file), 
                ctypes.byref(out_num_iterations),
                ctypes.byref(self.handle)))
            out_num_class = ctypes.c_int64(0)
            _safe_call(_LIB.LGBM_BoosterGetNumClasses(
                self.handle,
                ctypes.byref(out_num_class)))
            self.__num_class = out_num_class.value
        else:
            raise TypeError('At least need training dataset or model file to create booster instance')

    def __del__(self):
        if self.handle is not None and self.__is_manage_handle:
            _safe_call(_LIB.LGBM_BoosterFree(self.handle))

    def set_train_data_name(self, name):
        self.__train_data_name = name

    def add_valid(self, data, name):
        """Add an validation data

        Parameters
        ----------
        data : Dataset
            validation data
        name : String
            name of validation data
        """
        if data.predictor is not self.init_predictor:
            raise Exception("Add validation data failed, you should use same predictor for these data")
        _safe_call(_LIB.LGBM_BoosterAddValidData(
            self.handle,
            data.handle))
        self.valid_sets.append(data)
        self.name_valid_sets.append(name)
        self.__num_dataset += 1
        self.__inner_predict_buffer.append(None)
        self.__is_predicted_cur_iter.append(False)

    def reset_parameter(self, params):
        """Reset parameters for booster

        Parameters
        ----------
        params : dict
            params
        silent : boolean, optional
            Whether print messages during construction
        """
        if 'metric' in params:
            self.__need_reload_eval_info = True
        params_str = param_dict_to_str(params)
        if params_str:
            _safe_call(_LIB.LGBM_BoosterResetParameter(
                self.handle,
                c_str(params_str)))

    def update(self, train_set=None, fobj=None):
        """
        Update for one iteration
        Note: for multi-class task, the score is group by class_id first, then group by row_id
              if you want to get i-th row score in j-th class, the access way is score[j*num_data+i]
              and you should group grad and hess in this way as well
        Parameters
        ----------
        train_set : training data, None means use last training data
        fobj : function
            Customized objective function.

        Returns
        -------
        is_finished, bool
        """

        """need reset training data"""
        if train_set is not None and train_set is not self.train_set:
            if train_set.predictor is not self.init_predictor:
                raise Exception("Replace training data failed, you should use same predictor for these data")
            self.train_set = train_set
            _safe_call(_LIB.LGBM_BoosterResetTrainingData(
                self.handle, 
                self.train_set.handle))
            self.__inner_predict_buffer[0] = None
        is_finished = ctypes.c_int(0)
        if fobj is None:
            _safe_call(_LIB.LGBM_BoosterUpdateOneIter(
                self.handle, 
                ctypes.byref(is_finished)))
            self.__is_predicted_cur_iter = [False for _ in range(self.__num_dataset)]
            return is_finished.value == 1
        else:
            grad, hess = fobj(self.__inner_predict(0), self.train_set)
            return self.__boost(grad, hess)

    def __boost(self, grad, hess):
        """
        Boost the booster for one iteration, with customized gradient statistics.
        Note: for multi-class task, the score is group by class_id first, then group by row_id
              if you want to get i-th row score in j-th class, the access way is score[j*num_data+i]
              and you should group grad and hess in this way as well
        Parameters
        ----------
        grad : 1d numpy or 1d list
            The first order of gradient.
        hess : 1d numpy or 1d list
            The second order of gradient.

        Returns
        -------
        is_finished, bool
        """
        if not is_numpy_1d_array(grad):
            if is_1d_list(grad):
                grad = np.array(grad, dtype=np.float32, copy=False)
            else:
                raise TypeError("grad should be numpy 1d array or 1d list")
        if not is_numpy_1d_array(hess):
            if is_1d_list(hess):
                hess = np.array(hess, dtype=np.float32, copy=False)
            else:
                raise TypeError("hess should be numpy 1d array or 1d list")
        if len(grad) != len(hess):
            raise ValueError('grad / hess length mismatch: {} / {}'.format(len(grad), len(hess)))
        if grad.dtype != np.float32:
            grad = grad.astype(np.float32, copy=False)
        if hess.dtype != np.float32:
            hess = hess.astype(np.float32, copy=False)
        is_finished = ctypes.c_int(0)
        _safe_call(_LIB.LGBM_BoosterUpdateOneIterCustom(
            self.handle,
            grad.ctypes.data_as(ctypes.POINTER(ctypes.c_float)),
            hess.ctypes.data_as(ctypes.POINTER(ctypes.c_float)),
            ctypes.byref(is_finished)))
        self.__is_predicted_cur_iter = [False for _ in range(self.__num_dataset)]
        return is_finished.value == 1

    def rollback_one_iter(self):
        """
        Rollback one iteration
        """
        _safe_call(_LIB.LGBM_BoosterRollbackOneIter(
            self.handle))
        self.__is_predicted_cur_iter = [False for _ in range(self.__num_dataset)]

    def current_iteration(self):
        out_cur_iter = ctypes.c_int64(0)
        _safe_call(_LIB.LGBM_BoosterGetCurrentIteration(
            self.handle,
            ctypes.byref(out_cur_iter)))
        return out_cur_iter.value
    
    def eval(self, data, name, feval=None):
        """Evaluate for data

        Parameters
        ----------
        data : Dataset object
        name : name of data
        feval : function
            Custom evaluation function.
        Returns
        -------
        result: list
            Evaluation result list.
        """
        if not isinstance(data, Dataset):
            raise TypeError("Can only eval for Dataset instance")
        data_idx = -1
        if data is self.train_set:
            data_idx = 0
        else:
            for i in range(len(self.valid_sets)):
                if data is self.valid_sets[i]:
                    data_idx = i + 1
                    break
        """need push new valid data"""
        if data_idx == -1:
            self.add_valid(data, name)
            data_idx = self.__num_dataset - 1

        return self.__inner_eval(name, data_idx, feval)

    def eval_train(self, feval=None):
        """Evaluate for training data

        Parameters
        ----------
        feval : function
            Custom evaluation function.

        Returns
        -------
        result: str
            Evaluation result list.
        """
        return self.__inner_eval(self.__train_data_name, 0, feval)

    def eval_valid(self, feval=None):
        """Evaluate for validation data

        Parameters
        ----------
        feval : function
            Custom evaluation function.

        Returns
        -------
        result: str
            Evaluation result list.
        """
        ret = []
        for i in range(1, self.__num_dataset):
            ret.extend(self.__inner_eval(self.name_valid_sets[i-1], i, feval))
        return ret

    def save_model(self, filename, num_iteration=-1):
        """Save model of booster to file

        Parameters
        ----------
        filename : str
            filename to save 
        num_iteration: int
            number of iteration that want to save. < 0 means save all
        """
        _safe_call(_LIB.LGBM_BoosterSaveModel(
            self.handle,
            num_iteration,
            c_str(filename)))

    def predict(self, data, num_iteration=-1, raw_score=False, pred_leaf=False, data_has_header=False, is_reshape=True):
        """
        Predict logic

        Parameters
        ----------
        data : string/numpy array/scipy.sparse
            Data source for prediction
            When data is string type, it represents the path of txt file,
        num_iteration : 
            used iteration for prediction
        raw_score : bool 
            True for predict raw score
        pred_leaf : bool
            True for predict leaf index
        data_has_header : bool
            Used for txt data
        is_reshape : bool
            True for reshape to [nrow, ...] 

        Returns
        -------
        Prediction result
        """
        predictor = Predictor(booster_handle=self.handle, is_manage_handle=False)
        return predictor.predict(data, num_iteration, raw_score, pred_leaf, data_has_header, is_reshape)

    def to_predictor(self):
        """Convert to predictor
        Note: Predictor will manage the handle after doing this
        """
        predictor = Predictor(booster_handle=self.handle, is_manage_handle=True)
        self.__is_manage_handle = False
        return predictor

    def __inner_eval(self, data_name, data_idx, feval=None):
        """
        Evaulate training  or validation data
        """
        if data_idx >= self.__num_dataset:
            raise ValueError("data_idx should be smaller than number of dataset")
        self.__get_eval_info()
        ret = []
        if self.__num_inner_eval > 0:
            result = np.array([0.0 for _ in range(self.__num_inner_eval)], dtype=np.float32)
            tmp_out_len = ctypes.c_int64(0)
            _safe_call(_LIB.LGBM_BoosterGetEval(
                self.handle, 
                data_idx, 
                ctypes.byref(tmp_out_len), 
                result.ctypes.data_as(ctypes.POINTER(ctypes.c_float))))
            if tmp_out_len.value != self.__num_inner_eval:
                raise ValueError("incorrect number of eval results")
            for i in range(self.__num_inner_eval):
                ret.append((data_name, self.__name_inner_eval[i], result[i], self.__higher_better_inner_eval[i]))
        if feval is not None:
            if data_idx == 0:
                cur_data = self.train_set
            else:
                cur_data = self.valid_sets[data_idx - 1]
            feval_ret = feval(self.__inner_predict(data_idx), cur_data)
            if isinstance(feval_ret, list):
                for eval_name, val, is_higher_better in feval_ret:
                    ret.append((data_name, eval_name, val, is_higher_better))
            else:
                eval_name, val, is_higher_better = feval_ret
                ret.append((data_name, eval_name, val, is_higher_better))
        return ret

    def __inner_predict(self, data_idx):
        """
        Predict for training and validation dataset
        """
        if data_idx >= self.__num_dataset:
            raise ValueError("data_idx should be smaller than number of dataset")
        if self.__inner_predict_buffer[data_idx] is None:
            if data_idx == 0:
                n_preds = self.train_set.num_data() * self.__num_class
            else:
                n_preds = self.valid_sets[data_idx - 1].num_data() * self.__num_class
            self.__inner_predict_buffer[data_idx] = \
                np.array([0.0 for _ in range(n_preds)], dtype=np.float32, copy=False)
        """avoid to predict many time in one iteration"""
        if not self.__is_predicted_cur_iter[data_idx]:
            tmp_out_len = ctypes.c_int64(0)
            data_ptr = self.__inner_predict_buffer[data_idx].ctypes.data_as(ctypes.POINTER(ctypes.c_float))
            _safe_call(_LIB.LGBM_BoosterGetPredict(
                self.handle, 
                data_idx, 
                ctypes.byref(tmp_out_len), 
                data_ptr))
            if tmp_out_len.value != len(self.__inner_predict_buffer[data_idx]):
                raise ValueError("incorrect number of predict results for data %d" %(data_idx) )
            self.__is_predicted_cur_iter[data_idx] = True
        return self.__inner_predict_buffer[data_idx]

    def __get_eval_info(self):
        """
        Get inner evaluation count and names
        """
        if self.__need_reload_eval_info:
            self.__need_reload_eval_info = False
            out_num_eval = ctypes.c_int64(0)
            """Get num of inner evals"""
            _safe_call(_LIB.LGBM_BoosterGetEvalCounts(
                self.handle,
                ctypes.byref(out_num_eval)))
            self.__num_inner_eval = out_num_eval.value
            if self.__num_inner_eval > 0:
                """Get name of evals"""
                tmp_out_len = ctypes.c_int64(0)
                string_buffers = [ctypes.create_string_buffer(255) for i in range(self.__num_inner_eval)]
                ptr_string_buffers = (ctypes.c_char_p*self.__num_inner_eval)(*map(ctypes.addressof, string_buffers))
                _safe_call(_LIB.LGBM_BoosterGetEvalNames(
                    self.handle,
                    ctypes.byref(tmp_out_len),
                    ptr_string_buffers))
                if self.__num_inner_eval != tmp_out_len.value:
                    raise ValueError("size of eval names doesn't equal with num_evals")
                self.__name_inner_eval = []
                for i in range(self.__num_inner_eval):
                    self.__name_inner_eval.append(string_buffers[i].value.decode())
                self.__higher_better_inner_eval = []
                higher_better_metric = ['auc', 'ndcg']
                for name in self.__name_inner_eval:
                    if any(name.startswith(x) for x in higher_better_metric):
                        self.__higher_better_inner_eval.append(True)
                    else:
                        self.__higher_better_inner_eval.append(False)
    def attr(self, key):
        """Get attribute string from the Booster.

        Parameters
        ----------
        key : str
            The key to get attribute from.

        Returns
        -------
        value : str
            The attribute value of the key, returns None if attribute do not exist.
        """
        if key in self.__attr:
            return self.__attr[key]
        else:
            return None

    def set_attr(self, **kwargs):
        """Set the attribute of the Booster.

        Parameters
        ----------
        **kwargs
            The attributes to set. Setting a value to None deletes an attribute.
        """
        for key, value in kwargs.items():
            if value is not None:
                if not is_str(value):
                    raise ValueError("Set Attr only accepts string values")
                self.__attr[key] = value
            else:
                self.__attr.pop(key, None)