[Python-ideas] PEP for executing a module in a package containing relative imports (original) (raw)
Jacob Holm jh at improva.dk
Sun Apr 22 02:04:04 CEST 2007
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Ron Adam wrote:
Jacob Holm wrote: I find it very sad that PEP299 did in fact die, because I think it is much cleaner solution than the proposal that started this thread. That said, I would like to se a way to remove the name=='main' weirdness. I am +1 on resurrecting PEP299, but also +1 on adding a "sys.main" that could be used in a new "if name=sys.main". I am -1 on adding a builtin/global main as proposed, because that would clash with my own PEP299-like use of that name. I had at one time (about 4 years ago) thought it was a bit strange. But that was only for a very short while. To clarify: By "weirdness" here I meant the fact that the name of a module changes when it is used as the main module.
Python differs from other languages in a very important way. python always starts at the top of the file and works it way down until if falls off the bottom. What it does in between the top and the bottom is entirely up to you. It's very dynamic.
Other languages compile all the code first without executing any of it. Then you are required to tell the the compiler where the program will start, which is why you need to define a main() function. I know all that.
In Python, letting control fall off the bottom in order to start again at some place in the middle doesn't make much sense. It's already started, so you don't need to do that.
There are a number of reasons to want to use a function for the main part of the code, instead of putting it in an "if" at the end of the module. Two simple ones are:
Keeping the module namespace clean.
The ability to call the function from other code, most likely with different args.
Since I am usually writing such a function anyway, I would prefer not to have to write the "if" boilerplate at the bottom in order to get it called. Oh, and automatically calling a main function if it exists, does not prevent people who like the current "if" aproach from using that. It would just make my life that tiny bit easier.
Therefore I would like to keep that door open by not adding the proposed main variable at this point. Fortunately, the people that matter here seem to think avoiding the extra variable is a good idea (although for different reasons).
Jacob
-- Jacob Holm CTO Improva ApS
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