title: raspberry pi 4 cv2 and pandas importError
body: <p>If I import cv2 this happens:</p>
  <pre><code>pi4@pi:~ $ python
  Python 3.9.2 (default, Mar 12 2021, 04:06:34) 
  [GCC 10.2.1 20210110] on linux
  Type &quot;help&quot;, &quot;copyright&quot;, &quot;credits&quot; or &quot;license&quot; for more information.
  &gt;&gt;&gt; import cv2
  Traceback (most recent call last):
    File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
    File &quot;/usr/local/lib/python3.9/dist-packages/cv2/__init__.py&quot;, line 181, in &lt;module&gt;
      bootstrap()
    File &quot;/usr/local/lib/python3.9/dist-packages/cv2/__init__.py&quot;, line 153, in bootstrap
      native_module = importlib.import_module(&quot;cv2&quot;)
    File &quot;/usr/lib/python3.9/importlib/__init__.py&quot;, line 127, in import_module
      return _bootstrap._gcd_import(name[level:], package, level)
  ImportError: libcblas.so.3: cannot open shared object file: No such file or directory
  &gt;&gt;&gt; 
  </code></pre>
  <p>The module is installed and I tried everything, but nothing works.</p>
  <p>I have a raspberry pi 4 model b with the standard raspberry pi os and python version 3.9.2.</p>
  <p>Everything is up to date: the raspberry pi, pip and python.</p>
  <p>I tried many different commands to install cv2 with: <code>sudo pip3 install opencv-python</code>, <code>sudo pip install opencv-python</code>, <code>pip install opencv-python</code> and I tried <code>apt</code> also.</p>
  <p>The package is installed because i ran this command:</p>
  <pre><code>pi4@pi:~ $ pip install opencv-python
  Looking in indexes: https://pypi.org/simple, https://www.piwheels.org/simple
  Requirement already satisfied: opencv-python in /usr/local/lib/python3.9/dist-packages (4.6.0.66)
  Requirement already satisfied: numpy&gt;=1.17.3 in /usr/lib/python3/dist-packages (from opencv-python) (1.19.5)
  </code></pre>
  <p><strong>Important !:</strong></p>
  <p>I also can't import pandas:</p>
  <pre><code>pi4@pi:~ $ python
  Python 3.9.2 (default, Mar 12 2021, 04:06:34) 
  [GCC 10.2.1 20210110] on linux
  Type &quot;help&quot;, &quot;copyright&quot;, &quot;credits&quot; or &quot;license&quot; for more information.
  &gt;&gt;&gt; import pandas
  Traceback (most recent call last):
    File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
    File &quot;/home/pi4/.local/lib/python3.9/site-packages/pandas/__init__.py&quot;, line 22, in &lt;module&gt;
      from pandas.compat import is_numpy_dev as _is_numpy_dev
    File &quot;/home/pi4/.local/lib/python3.9/site-packages/pandas/compat/__init__.py&quot;, line 15, in &lt;module&gt;
      from pandas.compat.numpy import (
    File &quot;/home/pi4/.local/lib/python3.9/site-packages/pandas/compat/numpy/__init__.py&quot;, line 4, in &lt;module&gt;
      from pandas.util.version import Version
    File &quot;/home/pi4/.local/lib/python3.9/site-packages/pandas/util/__init__.py&quot;, line 1, in &lt;module&gt;
      from pandas.util._decorators import (  # noqa:F401
    File &quot;/home/pi4/.local/lib/python3.9/site-packages/pandas/util/_decorators.py&quot;, line 14, in &lt;module&gt;
      from pandas._libs.properties import cache_readonly  # noqa:F401
    File &quot;/home/pi4/.local/lib/python3.9/site-packages/pandas/_libs/__init__.py&quot;, line 13, in &lt;module&gt;
      from pandas._libs.interval import Interval
    File &quot;pandas/_libs/interval.pyx&quot;, line 1, in init pandas._libs.interval
  ValueError: numpy.ndarray size changed, may indicate binary incompatibility. Expected 48 from C header, got 40 from PyObject
  &gt;&gt;&gt; 
  </code></pre>
  <p>Is the problem that my raspberry pi is named pi4?</p>
  <p>Thanks in advice!</p>