title: Python: No module named ... How to use pip
body: <p>I'm a new to Python, and I have a trouble in import library.</p>
  
  <p>I wrote a code</p>
  
  <pre><code>from sklearn.linear_model import LogisticRegression
  </code></pre>
  
  <p>then I got an error</p>
  
  <pre><code>ImportError                               Traceback (most recent call last)
  &lt;ipython-input-19-c84b03903d9e&gt; in &lt;module&gt;()
  ----&gt; 1 from sklearn.linear_model import LogisticRegression
  
  /usr/lib/python2.7/dist-packages/sklearn/linear_model/__init__.py in &lt;module&gt;()
       10 # complete documentation.
       11 
  ---&gt; 12 from .base import LinearRegression
       13 
       14 from .bayes import BayesianRidge, ARDRegression
  
  /usr/lib/python2.7/dist-packages/sklearn/linear_model/base.py in &lt;module&gt;()
       22 
       23 from ..externals import six
  ---&gt; 24 from ..externals.joblib import Parallel, delayed
       25 from ..base import BaseEstimator, ClassifierMixin, RegressorMixin
       26 from ..utils import as_float_array, atleast2d_or_csr, safe_asarray
  
  /usr/lib/python2.7/dist-packages/sklearn/externals/joblib/__init__.py in &lt;module&gt;()
        1 # yoh: use system-wide joblib
        2 
  ----&gt; 3 from joblib import *
  
  ImportError: No module named joblib
  </code></pre>
  
  <p>in IPython.
  I'm using ubuntu and I installed scikit_learn-0.18 by using "sudo apt-get install python-sklearn" command but encountered above error.
  I also tried to use "sudo easy_install joblib" but the error was not erased.</p>
  
  <p>What is wrong? Would you help me? Thank you.</p>