gistfile1.py

from sklearn import preprocessing, pipeline

label_enc = preprocessing.LabelEncoder()
pipe = pipeline.Pipeline([('enc', label_enc)])

X = ['foo', 'bar', 'baz']

label_enc.fit(X) # works
pipe.fit(X) # fails w/ output below

'''
Output:

Traceback (most recent call last):
  File "pipetest.py", line 9, in <module>
    pipe.fit(X)
  File "/Library/Python/2.7/site-packages/sklearn/pipeline.py", line 128, in fit
    self.steps[-1][-1].fit(Xt, y, **fit_params)
TypeError: fit() takes exactly 2 arguments (3 given)
'''