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Fixing a note on encoding declaration, its usage in urlopen based on review

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comments from RDM and Ezio.
This commit is contained in:
Senthil Kumaran 2010-04-22 10:53:30 +00:00
parent 5e73a819ca
commit 0c2d8b8e51
1 changed files with 22 additions and 15 deletions
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37
Doc/library/urllib.request.rst
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@ -1072,30 +1072,37 @@ HTTPErrorProcessor Objects
Examples
--------
This example gets the python.org main page and displays the first 100 bytes of
This example gets the python.org main page and displays the first 300 bytes of
it. ::
>>> import urllib.request
>>> f = urllib.request.urlopen('http://www.python.org/')
>>> print(f.read(100))
b'<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<?xml-stylesheet href="./css/ht2html'
>>> print(f.read(300))
b'<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">\n\n\n<html
xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">\n\n<head>\n
<meta http-equiv="content-type" content="text/html; charset=utf-8" />\n
<title>Python Programming '
Note that in Python 3, urlopen returns a bytes object by default. In many
circumstances, you might expect the output of urlopen to be a string. This
might be a carried over expectation from Python 2, where urlopen returned
string or it might even the common usecase. In those cases, you should
explicitly decode the bytes to string.
Note that urlopen returns a bytes object. This is because there is no way
for urlopen to automatically determine the encoding of the byte stream
it receives from the http server. In general, a program will decode
the returned bytes object to string once it determines or guesses
the appropriate encoding.
In the examples below, we have chosen *utf-8* encoding for demonstration, you
might choose the encoding which is suitable for the webpage you are
requesting::
The following W3C document, http://www.w3.org/International/O-charset , lists
the various ways in which a (X)HTML or a XML document could have specified its
encoding information.
As python.org website uses *utf-8* encoding as specified in it's meta tag, we
will use same for decoding the bytes object. ::
>>> import urllib.request
>>> f = urllib.request.urlopen('http://www.python.org/')
>>> print(f.read(100).decode('utf-8')
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<?xml-stylesheet href="./css/ht2html
>>> print(fp.read(100).decode('utf-8'))
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtm
In the following example, we are sending a data-stream to the stdin of a CGI
and reading the data it returns to us. Note that this example will only work