lxml

Warning raised when using lxml.html.soupparser.fromstring

Bug #1752096 reported by Allan Hansen on 2018-02-27

This bug affects 1 person

Affects		Status	Importance	Assigned to	Milestone
	lxml	Triaged	Undecided	Unassigned

Bug Description

There's a warning raised when using lxml.html.soupparser.fromstring:

In [1]: from lxml.html.soupparser import fromstring

In [2]: s = """<!DOCTYPE html>
   ...: <html>
   ...: <head>
   ...: <title>Hi!</title>
   ...: </head>
   ...: <body>
   ...: Foobar
   ...: </body>
   ...: </html>"""

In [3]:

In [3]: fromstring(s)
/Users/allan/homeInstalled/miniconda3/envs/py36/lib/python3.6/site-packages/bs4/__init__.py:181: 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.

The code that caused this warning is on line 11 of the file /Users/allan/homeInstalled/miniconda3/envs/py36/bin/ipython. To get rid of this warning, change code that looks like this:

BeautifulSoup(YOUR_MARKUP})

to this:

BeautifulSoup(YOUR_MARKUP, "html.parser")

markup_type=markup_type))

I happen to know that the same warning is raised when using the BeautifulSoup library like so:

In [5]: from bs4 import BeautifulSoup
In [5]: from bs4 import BeautifulSoup

In [6]: s = """<!DOCTYPE html>
   ...: <html>
   ...: <head>
   ...: <title>Hej</title>
   ...: </head>
   ...: <body>
   ...: Foobar
   ...: </body>
   ...: </html>"""

In [7]: BeautifulSoup(s)
/Users/allan/homeInstalled/miniconda3/envs/py36/lib/python3.6/site-packages/bs4/__init__.py:181: UserWarning: No parser was explicitly specified, so I'm using the best available HTML parser for this system ("lxml"). 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.

The code that caused this warning is on line 11 of the file /Users/allan/homeInstalled/miniconda3/envs/py36/bin/ipython. To get rid of this warning, change code that looks like this:

BeautifulSoup(YOUR_MARKUP})

to this:

BeautifulSoup(YOUR_MARKUP, "lxml")

markup_type=markup_type))
Out[7]:
<!DOCTYPE html>
<html>
<head>
<title>Hej</title>
</head>
<body>
Foobar
</body>
</html>

In [8]: BeautifulSoup(s, 'lxml') # no warning raised
Out[8]:
<!DOCTYPE html>
<html>
<head>
<title>Hej</title>
</head>
<body>
Foobar
</body>
</html>

System information:

Python : sys.version_info(major=3, minor=6, micro=3, releaselevel='final', serial=0)
lxml.etree : (3, 8, 0, 0)
libxml used : (2, 9, 4)
libxml compiled : (2, 9, 4)
libxslt used : (1, 1, 29)
libxslt compiled : (1, 1, 29)