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enigma2 python coding rules
===========================
1.) The Zen of Python
The Zen of Python, by Tim Peters
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!
2.) Exceptions
Exceptions are great!
They are great to nullify any performance. Don't ever use them in functions
which are called more than once or twice.
Don't use them when a failure is expected. Use them for unexpected failures,
not as a method for coroutines.
C++ wrapped stuff usually doesn't throw exceptions, but returns None or
stuff like that.
Exceptions trough C++ are evil, too. Don't throw exceptions on callbacks
made from C++!
Exceptions are still great!
For example, to hide your coding errors. Don't wrap your code in a
try:/except:-clause because it behaves differently each time. The proper
solution is to fix your code!
Sometimes, exceptions are ok.
Really. For example, when opening a file, which you expect to be there. It's
ok if there is an assertion failure, i.e. something which can't be, unless
something is seriously broken (i.e. buggy, not misconfigured)!
As a rule of thumb,
"except:" (that is, without a specification which exception to catch) is
generally FORBIDDEN.
(Of course, unless you know what you're doing. So if you're feeling smarter
than this document, do whatever you like.)
3.) exec, eval, or other uses of dynamic code
Be aware that any call to exec/eval/... opens a backdoor. That sucks. Plus,
it starts the parser, which is SLOOOW. There are generally very few reasons
to call exec/eval.
- importing a "plugin", or resolving a dynamic reference (for example in a
menu.xml)
There is __import__. "exec 'import ' + string" is not so good.
- dynamically resolving function names
There is "getattr". For example an "eval('blub.' + x)" can also be written
as "blub.getattr(x)", which is a LOT faster as it doesn't need to start a
parser. It's also easier to debug.
- dynamic code, loaded from a menu.xml.
You can compile() code, and call that later. The backdoor warning still
applies, of course.
4.) formatting rules
Please use tabs (that is, \t) for indenting.
Empty lines should be either empty, or indented like the line before / line
after. Empty lines are definitely preferred to save bandwidth.
An ascii file ends with \n, and preferrable not with other empty lines.
That means: make sure the last line doesn't contain any characters, thanks.
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