Adam Mercer wrote: > Hi > > I'm trying to update one of my scripts so that it runs under python2 > and python3, but I'm running into an issue that the following example > illustrates: > > $ cat test.py > try: > # python-2.x > from urllib2 import urlopen > from ConfigParser import ConfigParser > except ImportError: > # python-3.x > from urllib.request import urlopen > from configparser import ConfigParser > > server='http://www.lsc-group.phys.uwm.edu/~ram/files' > > fp = urlopen('%s/latest.ini' % server).fp > cp = ConfigParser() > cp.readfp(fp) > print(cp.get('version', '10.8')) > $ > > This works as expected when using python2: > > $ python2.7 test.py > 5.2.10 > $ > > but when using python3 I receive the following error: > > $ python3.3 test.py > Traceback (most recent call last): > File "test.py", line 14, in <module> > cp.readfp(fp) > File > "/opt/local/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/configparser.py", > line 753, in readfp > self.read_file(fp, source=filename) > File > "/opt/local/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/configparser.py", > line 708, in read_file > self._read(f, source) > File > "/opt/local/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/configparser.py", > line 1010, in _read > for lineno, line in enumerate(fp, start=1): > ValueError: I/O operation on closed file. > $ > > Is there a way to get this working in both python2 and python3? > > This is a small script and I'm starting to have some users wanting to > use python3 and others sticking to python2 so I'd like to accommodate > them both if possible.
Python 3.3.0 (v3.3.0:bd8afb90ebf2, Sep 30 2012, 14:49:00) [GCC 4.6.1] on linux Type "help", "copyright", "credits" or "license" for more information. >>> from urllib.request import urlopen >>> url = "http://www.lsc-group.phys.uwm.edu/~ram/files/latest.ini"; >>> fp = urlopen(url).fp >>> fp.read() Traceback (most recent call last): File "<stdin>", line 1, in <module> ValueError: read of closed file >>> resp = urlopen(url) >>> resp.fp.read() b'[version]\n10.5 = 5.2.4\n10.6 = 5.2.10\n10.7 = 5.2.10\n10.8 = 5.2.10\n' I don't know whether this behaviour is intentional or accidental (I assume the latter). I then ran into another problem: >>> from configparser import ConfigParser >>> p = ConfigParser() >>> resp = urlopen(url) >>> p.readfp(resp.fp) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/local/lib/python3.3/configparser.py", line 754, in readfp self.read_file(fp, source=filename) File "/usr/local/lib/python3.3/configparser.py", line 709, in read_file self._read(f, source) File "/usr/local/lib/python3.3/configparser.py", line 1011, in _read if line.strip().startswith(prefix): TypeError: startswith first arg must be bytes or a tuple of bytes, not str So ConfigParser.readfp() (which has been deprecated in favour of read_file(), btw.) expects a text file: >>> from io import TextIOWrapper >>> resp = urlopen(url) >>> p.readfp(TextIOWrapper(resp.fp)) >>> p.get("version", "10.8") '5.2.10' Applying these findings to your script: from contextlib import contextmanager try: # python-2.x from urllib2 import urlopen from ConfigParser import ConfigParser @contextmanager def my_urlopen(url): yield urlopen(url).fp except ImportError: # python-3.x from urllib.request import urlopen from configparser import ConfigParser import io @contextmanager def my_urlopen(url): resp = urlopen(url) yield io.TextIOWrapper(resp.fp) server='http://www.lsc-group.phys.uwm.edu/~ram/files' cp = ConfigParser() with my_urlopen('%s/latest.ini' % server) as fp: cp.readfp(fp) print(cp.get('version', '10.8')) I've run it with 2.6, 2.7, 3.2, and 3.3. -- http://mail.python.org/mailman/listinfo/python-list
