问题描述
我定义了一个自定义的tansformer，它接受一个pandas数据框，仅在一个列上应用一个功能，而其余所有列保持不变。在测试过程中，该变压器工作正常，但是当我将其包含在管道中时却无法正常工作。
这是变压器：
import re
from sklearn.base import BaseEstimator,TransformerMixin
class SynopsisCleaner(BaseEstimator,TransformerMixin):
def __init__(self):
return None
def fit(self,X,y=None,**fit_params):
# nothing to learn from data.
return self
def clean_text(self,text):
text = text.lower()
text = re.sub(r'@[a-zA-Z0-9_]+','',text)
text = re.sub(r'https?://[A-Za-z0-9./]+',text)
text = re.sub(r'www.[^ ]+',text)
text = re.sub(r'[a-zA-Z0-9]*www[a-zA-Z0-9]*com[a-zA-Z0-9]*',text)
text = re.sub(r'[^a-zA-Z]',' ',text)
text = [token for token in text.split() if len(token) > 2]
text = ' '.join(text)
return text
def transform(self,**fit_params):
for i in range(X.shape[0]):
X[i] = self.clean_text(X[i])
return X
当我像这样手动测试时，它按预期运行。
train_synopsis = SynopsisCleaner().transform(train_data['Synopsis'])
但是，当我将其包含在sklearn管道中时：
from sklearn.compose import ColumnTransformer
from sklearn.pipeline import Pipeline
# part 1: defining a column transformer that learns on only one column and transforms it
synopsis_clean_col_tran = ColumnTransformer(transformers=[('synopsis_clean_col_tran',SynopsisCleaner(),['Synopsis'])],# set remainder to passthrough to pass along all the un-specified columns untouched to the next steps
remainder='passthrough')
# make a pipeline Now with all the steps
pipe_1 = Pipeline(steps=[('synopsis_cleaning',synopsis_clean_col_tran)])
pipe_1.fit(train_data)
我收到KeyError，如下所示：
---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
/usr/local/lib/python3.6/dist-packages/pandas/core/indexes/base.py in get_loc(self,key,method,tolerance)
2890 try:
-> 2891 return self._engine.get_loc(casted_key)
2892 except KeyError as err:
pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()
pandas/_libs/index.pyx in pandas._libs.index.IndexEngine.get_loc()
pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()
pandas/_libs/hashtable_class_helper.pxi in pandas._libs.hashtable.PyObjectHashTable.get_item()
KeyError: 0
The above exception was the direct cause of the following exception:
KeyError Traceback (most recent call last)
16 frames
<ipython-input-10-3396fa5d6092> in <module>()
6 # make a pipeline Now with all the steps
7 pipe_1 = Pipeline(steps=[('synopsis_cleaning',synopsis_clean_col_tran)])
----> 8 pipe_1.fit(train_data)
/usr/local/lib/python3.6/dist-packages/sklearn/pipeline.py in fit(self,y,**fit_params)
352 self._log_message(len(self.steps) - 1)):
353 if self._final_estimator != 'passthrough':
--> 354 self._final_estimator.fit(Xt,**fit_params)
355 return self
356
/usr/local/lib/python3.6/dist-packages/sklearn/compose/_column_transformer.py in fit(self,y)
482 # we use fit_transform to make sure to set sparse_output_ (for which we
483 # need the transformed data) to have consistent output type in predict
--> 484 self.fit_transform(X,y=y)
485 return self
486
/usr/local/lib/python3.6/dist-packages/sklearn/compose/_column_transformer.py in fit_transform(self,y)
516 self._validate_remainder(X)
517
--> 518 result = self._fit_transform(X,_fit_transform_one)
519
520 if not result:
/usr/local/lib/python3.6/dist-packages/sklearn/compose/_column_transformer.py in _fit_transform(self,func,fitted)
455 message=self._log_message(name,idx,len(transformers)))
456 for idx,(name,trans,column,weight) in enumerate(
--> 457 self._iter(fitted=fitted,replace_strings=True),1))
458 except ValueError as e:
459 if "Expected 2D array,got 1D array instead" in str(e):
/usr/local/lib/python3.6/dist-packages/joblib/parallel.py in __call__(self,iterable)
1027 # remaining jobs.
1028 self._iterating = False
-> 1029 if self.dispatch_one_batch(iterator):
1030 self._iterating = self._original_iterator is not None
1031
/usr/local/lib/python3.6/dist-packages/joblib/parallel.py in dispatch_one_batch(self,iterator)
845 return False
846 else:
--> 847 self._dispatch(tasks)
848 return True
849
/usr/local/lib/python3.6/dist-packages/joblib/parallel.py in _dispatch(self,batch)
763 with self._lock:
764 job_idx = len(self._jobs)
--> 765 job = self._backend.apply_async(batch,callback=cb)
766 # A job can complete so quickly than its callback is
767 # called before we get here,causing self._jobs to
/usr/local/lib/python3.6/dist-packages/joblib/_parallel_backends.py in apply_async(self,callback)
206 def apply_async(self,callback=None):
207 """Schedule a func to be run"""
--> 208 result = ImmediateResult(func)
209 if callback:
210 callback(result)
/usr/local/lib/python3.6/dist-packages/joblib/_parallel_backends.py in __init__(self,batch)
570 # Don't delay the application,to avoid keeping the input
571 # arguments in memory
--> 572 self.results = batch()
573
574 def get(self):
/usr/local/lib/python3.6/dist-packages/joblib/parallel.py in __call__(self)
251 with parallel_backend(self._backend,n_jobs=self._n_jobs):
252 return [func(*args,**kwargs)
--> 253 for func,args,kwargs in self.items]
254
255 def __reduce__(self):
/usr/local/lib/python3.6/dist-packages/joblib/parallel.py in <listcomp>(.0)
251 with parallel_backend(self._backend,kwargs in self.items]
254
255 def __reduce__(self):
/usr/local/lib/python3.6/dist-packages/sklearn/pipeline.py in _fit_transform_one(transformer,weight,message_clsname,message,**fit_params)
726 with _print_elapsed_time(message_clsname,message):
727 if hasattr(transformer,'fit_transform'):
--> 728 res = transformer.fit_transform(X,**fit_params)
729 else:
730 res = transformer.fit(X,**fit_params).transform(X)
/usr/local/lib/python3.6/dist-packages/sklearn/base.py in fit_transform(self,**fit_params)
569 if y is None:
570 # fit method of arity 1 (unsupervised transformation)
--> 571 return self.fit(X,**fit_params).transform(X)
572 else:
573 # fit method of arity 2 (supervised transformation)
<ipython-input-6-004ee595d544> in transform(self,**fit_params)
20 def transform(self,**fit_params):
21 for i in range(X.shape[0]):
---> 22 X[i] = self.clean_text(X[i])
23 return X
/usr/local/lib/python3.6/dist-packages/pandas/core/frame.py in __getitem__(self,key)
2900 if self.columns.nlevels > 1:
2901 return self._getitem_multilevel(key)
-> 2902 indexer = self.columns.get_loc(key)
2903 if is_integer(indexer):
2904 indexer = [indexer]
/usr/local/lib/python3.6/dist-packages/pandas/core/indexes/base.py in get_loc(self,tolerance)
2891 return self._engine.get_loc(casted_key)
2892 except KeyError as err:
-> 2893 raise KeyError(key) from err
2894
2895 if tolerance is not None:
KeyError: 0
我在做什么错了？
编辑1：，不带方括号，列名指定为字符串，这是我看到的错误：
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-11-bdd42b09e2af> in <module>()
6 # make a pipeline Now with all the steps
7 pipe_1 = Pipeline(steps=[('synopsis_cleaning',synopsis_clean_col_tran)])
----> 8 pipe_1.fit(train_data)
3 frames
/usr/local/lib/python3.6/dist-packages/sklearn/pipeline.py in fit(self,y)
536
537 self._update_fitted_transformers(transformers)
--> 538 self._validate_output(Xs)
539
540 return self._hstack(list(Xs))
/usr/local/lib/python3.6/dist-packages/sklearn/compose/_column_transformer.py in _validate_output(self,result)
400 raise ValueError(
401 "The output of the '{0}' transformer should be 2D (scipy "
--> 402 "matrix,array,or pandas DataFrame).".format(name))
403
404 def _validate_features(self,n_features,feature_names):
ValueError: The output of the 'synopsis_clean_col_tran' transformer should be 2D (scipy matrix,or pandas DataFrame).
解决方法
在手动测试中，您通过了系列 train_data['Synopsis']，但列变换器正在通过 Frame train_data[['Synopsis']]。 （因此，为弄清错误：X[i]试图获取名为0的列，该列确实不存在。）您应该能够像将括号放在括号中一样容易地解决此问题。变压器的列规格中的'Synopsis'。 From the docs：
...如果转换器期望X为一维数组（矢量），则应使用标量字符串或整数，否则会将二维数组传递给转换器。 ...
也就是说，
synopsis_clean_col_tran = ColumnTransformer(
transformers=[('synopsis_clean_col_tran',SynopsisCleaner(),'Synopsis')],# set remainder to passthrough to pass along all the un-specified columns untouched to the next steps
remainder='passthrough',)
Ah，但随后ColumnTransformer抱怨您的变压器的输出是一维的；那真不幸。我认为当时最干净的方法是切换您的transform以同时将输入和输出都视为2D。如果您只需要数据帧作为输入（没有其他sklearn转换器转换为numpy数组），那么使用FunctionTransformer而不是自定义类可以相对简单。
def clean_text_frame(X):
return X.applymap(clean_text) # the function "clean_text" currently in your class.
synopsis_clean_col_tran = ColumnTransformer(
transformers=[('synopsis_clean_col_tran',FunctionTransformer(clean_text_frame),['Synopsis'])],)