How to get rid of BeautifulSoup user warning?

After I installed BeautifulSoup, Whenever I run my Python in cmd, this warning comes out.

D:\Application\python\lib\site-packages\beautifulsoup4-4.4.1-py3.4.egg\bs4\__init__.py:166:
UserWarning: No parser was explicitly specified, so I'm using the best
available HTML parser for this system ("html.parser"). This usually isn't a
problem, but if you run this code on another system, or in a different
virtual environment, it may use a different parser and behave differently.

To get rid of this warning, change this:

 BeautifulSoup([your markup])

to this:

 BeautifulSoup([your markup], "html.parser")

I have no ideal why it comes out and how to solve it.

The solution to your problem is clearly stated in the error message. Code like the below does not specify an XML/HTML/etc. parser.

BeautifulSoup( ... )

In order to fix the error, you'll need to specify which parser you'd like to use, like so:

BeautifulSoup( ..., "html.parser" )

You can also install a 3rd party parser if you'd like.

Documentation recommends that you install and use lxml for speed.

BeautifulSoup(html, "lxml")

> If you’re using a version of Python 2 earlier than 2.7.3, or a version > of Python 3 earlier than 3.2.2, it’s essential that you install lxml > or html5lib–Python’s built-in HTML parser is just not very good in > older versions.

Installing LXML parser

• On Ubuntu (debian)

   apt-get install python-lxml 
  

• Fedora (RHEL based)

   dnf install python-lxml
  

• Using PIP

   pip install lxml
  

For HTML parser, you need to install html5lib, run:

pip install html5lib

then add html5lib in the BeautifulSoup method:

htmlDoc = bs4.BeautifulSoup(req1.text, 'html5lib')
print(htmlDoc)

In my opinion, the previous posts did not answer the question.

Yes, as everyone said, you can remove the warning by specifying the parser.
And as pointed by the documentation, it is a best-practice for performances ¹ and for consistency ².

But in some cases, you want to silence the warning... Hence this post.

• since BeautifulSoup 4 rev 460, the warning message does not appear in interactive (REPL) mode
• there are more generalist answers at: https://stackoverflow.com/questions/14463277 to control Python warnings (TL;DL: PYTHONWARNINGS=ignore or -Wignore)
• suppressing the warning explicitly (bs4 ≥ rev 569) by adding to your code:

  import warnings
  warnings.filterwarnings('ignore', category=GuessedAtParserWarning)
  

• cheating by letting bs4 think you provided the parser, i.e.:

  bs4.BeautifulSoup(
    your_markup,
    builder=bs4.builder_registry.lookup(*bs4.BeautifulSoup.DEFAULT_BUILDER_FEATURES)
  )