opencv -python

https://www.python----------tab.com/html/2017/pythonhexinbiancheng_1120/1184.html

http://www.cnblogs.com/pmars/p/4143158.html---barcode

pip show  pytesseract

python -v *.py

And When I ran $python -v example.py, I found the referenced packages path hadn't been same with upper pytesseract package directory.

cf.

installed pytesseract path : /usr/local/lib/python3.5/dist-packages/pytesseract

actual referenced lib path, when running : /usr/lib/python2.7/dist-packages/

So, I copied pytesseract, located in "/usr/local/lib/python3.5/dist-packages/pytesseract" to "/usr/lib/python2.7/dist-packages/"

Then, Solved!