============ configparser ============ The ancient ``ConfigParser`` module available in the standard library 2.x has seen a major update in Python 3.2. This is a backport of those changes so that they can be used directly in Python 2.6 - 2.7. To use ``configparser`` instead of ``ConfigParser``, simply replace:: import ConfigParser with:: import configparser For detailed documentation consult the vanilla version at http://docs.python.org/3/library/configparser.html. Why you'll love ``configparser`` -------------------------------- Whereas almost completely compatible with its older brother, ``configparser`` sports a bunch of interesting new features: * full mapping protocol access (`more info `_):: >>> parser = ConfigParser() >>> parser.read_string(""" [DEFAULT] location = upper left visible = yes editable = no color = blue [main] title = Main Menu color = green [options] title = Options """) >>> parser['main']['color'] 'green' >>> parser['main']['editable'] 'no' >>> section = parser['options'] >>> section['title'] 'Options' >>> section['title'] = 'Options (editable: %(editable)s)' >>> section['title'] 'Options (editable: no)' * there's now one default ``ConfigParser`` class, which basically is the old ``SafeConfigParser`` with a bunch of tweaks which make it more predictable for users. Don't need interpolation? Simply use ``ConfigParser(interpolation=None)``, no need to use a distinct ``RawConfigParser`` anymore. * the parser is highly `customizable upon instantiation `__ supporting things like changing option delimiters, comment characters, the name of the DEFAULT section, the interpolation syntax, etc. * you can easily create your own interpolation syntax but there are two powerful implementations built-in (`more info `__): * the classic ``%(string-like)s`` syntax (called ``BasicInterpolation``) * a new ``${buildout:like}`` syntax (called ``ExtendedInterpolation``) * fallback values may be specified in getters (`more info `__):: >>> config.get('closet', 'monster', ... fallback='No such things as monsters') 'No such things as monsters' * ``ConfigParser`` objects can now read data directly `from strings `__ and `from dictionaries `__. That means importing configuration from JSON or specifying default values for the whole configuration (multiple sections) is now a single line of code. Same goes for copying data from another ``ConfigParser`` instance, thanks to its mapping protocol support. * many smaller tweaks, updates and fixes A few words about Unicode ------------------------- ``configparser`` comes from Python 3 and as such it works well with Unicode. The library is generally cleaned up in terms of internal data storage and reading/writing files. There are a couple of incompatibilities with the old ``ConfigParser`` due to that. However, the work required to migrate is well worth it as it shows the issues that would likely come up during migration of your project to Python 3. The design assumes that Unicode strings are used whenever possible [1]_. That gives you the certainty that what's stored in a configuration object is text. Once your configuration is read, the rest of your application doesn't have to deal with encoding issues. All you have is text [2]_. The only two phases when you should explicitly state encoding is when you either read from an external source (e.g. a file) or write back. Versioning ---------- This backport is intended to keep 100% compatibility with the vanilla release in Python 3.2+. To help maintaining a version you want and expect, a versioning scheme is used where: * the first three numbers indicate the version of Python 3.x from which the backport is done * a backport release number is provided after the ``r`` letter For example, ``3.3.0r1`` is the **first** release of ``configparser`` compatible with the library found in Python **3.3.0**. A single exception from the 100% compatibility principle is that bugs fixed before releasing another minor Python 3.x.y version **will be included** in the backport releases done in the mean time. This rule applies to bugs only. Maintenance ----------- This backport is maintained on BitBucket by Łukasz Langa, the current vanilla ``configparser`` maintainer for CPython: * `configparser Mercurial repository `_ * `configparser issue tracker `_ Change Log ---------- 3.3.0r2 ~~~~~~~ * updated the fix for `#16820 `_: parsers now preserve section order when using ``__setitem__`` and ``update`` 3.3.0r1 ~~~~~~~ * compatible with 3.3.0 + fixes for `#15803 `_ and `#16820 `_ * fixes `BitBucket issue #4 `_: ``read()`` properly treats a bytestring argument as a filename * `ordereddict `_ dependency required only for Python 2.6 * `unittest2 `_ explicit dependency dropped. If you want to test the release, add ``unittest2`` on your own. 3.2.0r3 ~~~~~~~ * proper Python 2.6 support * explicitly stated the dependency on `ordereddict `_ * numbered all formatting braces in strings * explicitly says that Python 2.5 support won't happen (too much work necessary without abstract base classes, string formatters, the ``io`` library, etc.) * some healthy advertising in the README 3.2.0r2 ~~~~~~~ * a backport-specific change: for convenience and basic compatibility with the old ConfigParser, bytestrings are now accepted as section names, options and values. Those strings are still converted to Unicode for internal storage so in any case when such conversion is not possible (using the 'ascii' codec), UnicodeDecodeError is raised. 3.2.0r1 ~~~~~~~ * the first public release compatible with 3.2.0 + fixes for `#11324 `_, `#11670 `_ and `#11858 `_. Conversion Process ------------------ This section is technical and should bother you only if you are wondering how this backport is produced. If the implementation details of this backport are not important for you, feel free to ignore the following content. ``configparser`` is converted using `3to2 `_. Because a fully automatic conversion was not doable, I took the following branching approach: * the ``3.x`` branch holds unchanged files synchronized from the upstream CPython repository. The synchronization is currently done by manually copying the required files and stating from which CPython changeset they come from. * the ``3.x-clean`` branch holds a version of the ``3.x`` code with some tweaks that make it independent from libraries and constructions unavailable on 2.x. Code on this branch still *must* work on the corresponding Python 3.x. You can check this running the supplied unit tests. * the ``default`` branch holds necessary changes which break unit tests on Python 3.2. Additional files which are used by the backport are also stored here. The process works like this: 1. I update the ``3.x`` branch with new versions of files. Commit. 2. I merge the new commit to ``3.x-clean``. Check unit tests. Commit. 3. If there are necessary changes that can be made in a 3.x compatible manner, I do them now (still on ``3.x-clean``), check unit tests and commit. If I'm not yet aware of any, no problem. 4. I merge the changes from ``3.x-clean`` to ``default``. Commit. 5. If there are necessary changes that *cannot* be made in a 3.x compatible manner, I do them now (on ``default``). Note that the changes should still be written using 3.x syntax. If I'm not yet aware of any required changes, no problem. 6. I run ``./convert.py`` which is a custom ``3to2`` runner for this project. 7. I run the unit tests with ``unittest2`` on Python 2.x. If the tests are OK, I can prepare a new release. Otherwise, I revert the ``default`` branch to its previous state (``hg revert .``) and go back to Step 3. **NOTE:** the ``default`` branch holds unconverted code. This is because keeping the conversion step as the last (after any custom changes) helps managing the history better. Plus, the merges are nicer and updates of the converter software don't create nasty conflicts in the repository. This process works well but if you have any tips on how to make it simpler and faster, do enlighten me :) Footnotes --------- .. [1] To somewhat ease migration, passing bytestrings is still supported but they are converted to Unicode for internal storage anyway. This means that for the vast majority of strings used in configuration files, it won't matter if you pass them as bytestrings or Unicode. However, if you pass a bytestring that cannot be converted to Unicode using the naive ASCII codec, a ``UnicodeDecodeError`` will be raised. This is purposeful and helps you manage proper encoding for all content you store in memory, read from various sources and write back. .. [2] Life gets much easier when you understand that you basically manage **text** in your application. You don't care about bytes but about letters. In that regard the concept of content encoding is meaningless. The only time when you deal with raw bytes is when you write the data to a file. Then you have to specify how your text should be encoded. On the other end, to get meaningful text from a file, the application reading it has to know which encoding was used during its creation. But once the bytes are read and properly decoded, all you have is text. This is especially powerful when you start interacting with multiple data sources. Even if each of them uses a different encoding, inside your application data is held in abstract text form. You can program your business logic without worrying about which data came from which source. You can freely exchange the data you store between sources. Only reading/writing files requires encoding your text to bytes.