ImportError: No module named bs4 - despite bs4 and BeautifulSoup being installed
Just pip install bs4. 
Probably, you are maintaining different versions of Python.
I downloaded Python 3.7 and am  running a script with "from bs4 import BeautifulSoup" and am receiving the following error on execution;

"File "myscript.py", line 3, in 
      from bs4 import BeautifulSoup ImportError: No module named bs4"

When I type "pip3 install bs4" or "pip3 install BeautifulSoup4" in the terminal I get the following;

"Requirement already satisfied: bs4 in
  /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages
  (0.0.1) Requirement already satisfied: beautifulsoup4 in
  /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages
  (from bs4) (4.6.3)"

Executing "import bs4" and "from bs4 import BeautifulSoup" in IDLE don't error out.
Any idea about what's going on?