title: TFIDF Vectorizer giving error
body: <p>I am trying to carry out text classification for certain files using TFIDF and SVM. The features are to be selected 3 words at a time . 
  My data files is already in the format :  angel eyes has, each one for, on its own.
  There are no stop words and neither can do lemming or stemming.
  I want the feature to be selected as: angel eyes has ...
  The code that I have written is given below:</p>
  
  <pre><code>import os
  import sys
  import numpy
  from sklearn.svm import LinearSVC
  from sklearn.metrics import confusion_matrix
  from sklearn.feature_extraction.text import CountVectorizer
  from sklearn.feature_extraction.text import TfidfTransformer
  from sklearn.feature_extraction.text import TfidfVectorizer
  from sklearn import metrics
  from sklearn.datasets import load_files
  from sklearn.cross_validation import train_test_split
  
  dt=load_files('C:/test4',load_content=True)
  d= len(dt)
  print dt.target_names
  X, y = dt.data, dt.target
  print y
  X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=0)
  print y_train
  vectorizer = CountVectorizer()
  z= vectorizer.fit_transform(X_train)
  tfidf_vect= TfidfVectorizer(lowercase= True, tokenizer=',', max_df=1.0, min_df=1, max_features=None, norm=u'l2', use_idf=True, smooth_idf=True, sublinear_tf=False)
  
  
  X_train_tfidf = tfidf_vect.fit_transform(z)
  
  print tfidf_vect.get_feature_names()
  svm_classifier = LinearSVC().fit(X_train_tfidf, y_train)
  </code></pre>
  
  <p>Unfortunately I am getting an error at"  X_train_tfidf = tfidf_vect.fit_transform(z)" :
                         AttributeError: lower not found .<br>
  If I modifiy code to do </p>
  
  <pre><code>tfidf_vect= TfidfVectorizer( tokenizer=',', use_idf=True, smooth_idf=True, sublinear_tf=False)
  print "okay2"
  #X_train_tfidf = tfidf_transformer.fit_transform(z)
  X_train_tfidf = tfidf_vect.fit_transform(X_train)
  print X_train_tfidf.getfeature_names()
  </code></pre>
  
  <p>I get the error  :  TypeError: 'str' object is not callable
  Can please someone tell me where am I going wrong</p>