need the best solution

import sklearn

X = sklearn.preprocessing.StandardScaler().fit_transform(X)


NameError                                 Traceback (most recent call last)
<ipython-input-3-e6c12a5cdab4> in <module>
      1 import sklearn
      2 
----> 3 X = sklearn.preprocessing.StandardScaler().fit_transform(X)

NameError: name 'X' is not defined