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urllib in python 3.1

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Join Date: Aug 2009

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Lingson

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urllib in python 3.1

Aug 22nd, 2009

hi, i've tried to search any examples to understand more about how to use the urllib in python 3.1, but all the tutorials are for python 2.x

i need to do just a simple thing like getting the text (as string) and manipulate it.

the code in python 2.x would be like:

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 Python Syntax (Toggle Plain Text) 
import urllib
url = 'http://www.pythonchallenge.com/pc/def/linkedlist.php?nothing=12345'
text = urllib.urlopen(url).read()
import urllib
url = 'http://www.pythonchallenge.com/pc/def/linkedlist.php?nothing=12345'
text = urllib.urlopen(url).read()

but when i tried it in python 3.1 (with urllib.request) like this:

 Help with Code Tags 
 Python Syntax (Toggle Plain Text) 
import urllib.request
url = 'http://www.pythonchallenge.com/pc/def/linkedlist.php?nothing='
current = '12345'
response = urllib.request.urlopen(url+current)
text = response.read()
current = text[-5:]
response = urllib.request.urlopen(url+current)
import urllib.request
url = 'http://www.pythonchallenge.com/pc/def/linkedlist.php?nothing='
current = '12345'
response = urllib.request.urlopen(url+current)
text = response.read()
current = text[-5:]
response = urllib.request.urlopen(url+current)

it gives me an error:
Can't convert 'bytes' object to str implicitly

i then look into the value of 'text' which turns out to be something like b'........' which means its a binary value.

from what i read and understand from the tutorials about urllib in python 2.x, when you do the urllib....read(), it gives you back a string.

i tried to convert the binary to string with binascii.b2a_uu(html), but the result is even more catastrophic.

can anyone please help how i can do this thing? thank you.

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Join Date: Jul 2005

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bumsfeld

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Re: urllib in python 3.1

Aug 22nd, 2009

One rude awakening with Python3 will be the frequent use of bytearrays instead of strings. It does this to handle international unicode better.

Here is how you deal with this:

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 python Syntax (Toggle Plain Text) 
# get code of given URL as html text string
# Python3 uses urllib.request.urlopen()
# instead of Python2's urllib.urlopen() or urllib2.urlopen()
 
import urllib.request
 
fp = urllib.request.urlopen("http://www.python.org")
 
mybytes = fp.read()
# note that Python3 does not read the html code as string
# but as html code bytearray, convert to string with
mystr = mybytes.decode("utf8")
 
fp.close()
 
print(mystr)
# get code of given URL as html text string
# Python3 uses urllib.request.urlopen()
# instead of Python2's urllib.urlopen() or urllib2.urlopen()

import urllib.request

fp = urllib.request.urlopen("http://www.python.org")

mybytes = fp.read()
# note that Python3 does not read the html code as string
# but as html code bytearray, convert to string with
mystr = mybytes.decode("utf8")

fp.close()

print(mystr)

Last edited by bumsfeld; Aug 22nd, 2009 at 11:39 am.

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Join Date: Aug 2009

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Lingson

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Re: urllib in python 3.1

Aug 22nd, 2009

ugh.. the solution was so easy? *lol*

one more question then:
is it safe to say that everytime i want to convert bytearrays to string i just need to use the .decode('utf8')?
(you are right with what you said about python 3 use more bytearrays than string. until now whenever that happen, i just try to use other way to overcome the problem since i cant find a way to convert it (base on info from python doc)).

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Join Date: Oct 2004

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vegaseat

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Re: urllib in python 3.1

Aug 23rd, 2009

UTF8 is pretty much the defacto standard for decoding in Python. However there may be other standards on the internet, depending on the country and its native language.

In this particular case ( http://www.python.org ), you can find the encoding used in this line:

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Python Syntax (Toggle Plain Text)

  <meta http-equiv="content-type" content="text/html; charset=utf-8" />

However, if you go for instance to a German website (http://www.python-forum.de), you will find this line:

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Python Syntax (Toggle Plain Text)

<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">

Last edited by vegaseat; Aug 23rd, 2009 at 2:37 pm. Reason: html code

May 'the Google' be with you!

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scru

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Re: urllib in python 3.1

Aug 23rd, 2009

•

Originally Posted by Lingson

ugh.. the solution was so easy? *lol*

one more question then:
is it safe to say that everytime i want to convert bytearrays to string i just need to use the .decode('utf8')?...some other stuff...

No, please don't do that.

That is okay if the page you are reading is encoded in ascii or utf-8. But if it is encoded in latin-1 (a fairly common encoding in its own right), you can run into trouble with non-ascii characters (like é for example)). And this is just for sites in languages based on latin script.

What you have to do is get the encoding from the server. The web server sends out the encoding that it uses* in the http header. The general idea is that the pages it serves would use that encoding.

* If only it were that simple. Sometimes the pages on the web server itself are encoded using a different encoding than what the web server is set to report (blame it on lazy, inconsistent webmasters?) Ideally, these pages have their encoding specified in their HTML headers.

Oh right, you were looking for a solution? I generally start decoding with the encoding that the http header specifies, but if the page's html header specifies a different encoding, I start over again with that new encoding. And if all else fails, either fall back to utf8 or refuse to decode all together. I know it sounds overly complicated (it probably is) but it's worth not having your application crash as soon as it's given a page not encoded with the one codec you hard coded.

I have a class that does this somewhere, but I can't find it...

Last edited by scru; Aug 23rd, 2009 at 12:21 pm.

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Join Date: Aug 2009

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Lingson

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Re: urllib in python 3.1

Aug 23rd, 2009

ok.. i get the point..

huh, i guess there are no such thing as beginners luck in python :-p

Last edited by Lingson; Aug 23rd, 2009 at 2:06 pm.

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vegaseat

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Re: urllib in python 3.1

Aug 23rd, 2009

As Scru mentioned, let's hope the authors of the website were good guys and included the type of encoding. You can modify Henri's code ...

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
# get the code of a given URL as html text string
# Python3 uses urllib.request.urlopen()
# get the encoding used first
# tested with Python 3.1 with the Editra IDE
 
import urllib.request
 
def extract(text, sub1, sub2):
    """
    extract a substring from text between first
    occurances of substrings sub1 and sub2
    """
    return text.split(sub1, 1)[-1].split(sub2, 1)[0]
 
 
fp = urllib.request.urlopen("http://www.python.org")
 
mybytes = fp.read()
 
encoding = extract(str(mybytes).lower(), 'charset=', '"')
print('-'*50)
print( "Encoding type = %s" % encoding )
print('-'*50)
 
if encoding:
    # note that Python3 does not read the html code as string
    # but as html code bytearray, convert to string with
    mystr = mybytes.decode(encoding)
    print(mystr)
else:
    print("Encoding type not found!")
 
 
fp.close()
# get the code of a given URL as html text string
# Python3 uses urllib.request.urlopen()
# get the encoding used first
# tested with Python 3.1 with the Editra IDE

import urllib.request

def extract(text, sub1, sub2):
    """
    extract a substring from text between first
    occurances of substrings sub1 and sub2
    """
    return text.split(sub1, 1)[-1].split(sub2, 1)[0]


fp = urllib.request.urlopen("http://www.python.org")

mybytes = fp.read()

encoding = extract(str(mybytes).lower(), 'charset=', '"')
print('-'*50)
print( "Encoding type = %s" % encoding )
print('-'*50)

if encoding:
    # note that Python3 does not read the html code as string
    # but as html code bytearray, convert to string with
    mystr = mybytes.decode(encoding)
    print(mystr)
else:
    print("Encoding type not found!")


fp.close()

May 'the Google' be with you!

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Join Date: Aug 2009

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Lingson

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Re: urllib in python 3.1

Aug 23rd, 2009

amazing..

thanks a lot guys.. really appreciate all your help..

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Re: urllib in python 3.1

Aug 25th, 2009

Not sure if this is a proper method or not but I havn't had any problems so far using....

 Help with Code Tags 
 python Syntax (Toggle Plain Text) 
x = repr(request.urlopen(req).read())
print(x)
x = repr(request.urlopen(req).read())
print(x)

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scru

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Re: urllib in python 3.1

#10

Aug 25th, 2009

•

Originally Posted by willygstyle

Not sure if this is a proper method or not but I havn't had any problems so far using....
Help with Code Tags

python Syntax (Toggle Plain Text)
x = repr(request.urlopen(req).read())
print(x)
x = repr(request.urlopen(req).read()) print(x)

You may want to take a second look at what that actually does...