String interpolation question

[Fernando Pérez]

Geoff Gerrietts wrote:

>> but I don't want that because in my real problem, the string is long and I
>> don't want the dangers of positionally matched %s arguments.
> 
> Given your constraints, I think I'd prefer:
> 
>>>> print "%(val1)s" % { 'val1': y[i] }
> 
> Or if you insist on using locals() (a habit I find at least as
> dangerous as positional arguments):
> 
>>>> z = y[i]
>>>> print '%(z)s' % locals()
> 6
> 
> On the other hand, if you're looking at a long y and multiple values
> of i (though your example provides no such hint), I'd prefer:
> 
> d = {}
> for indx in range(len(y))
>   d['y_%d'%indx] = y[indx]
> d.update(locals())
> 
> s = '%%(y_%d)s' % (i,)
> print s % d
> 
> If none of these solutions seem to satisfy your needs, maybe you
> should be a little more explicit about the problem domain. If one of
> the requirements is that it be a one-liner, I'm not sure if I can
> help.

Thanks for your suggestions. Basically imagine having many arrays and needing 
to generate output of the form (this is perl syntax, which for once is a 
million times cleaner than python for _this_ problem):

print "$i arr1[$i]=$arr1[$i] arr2[$i]=$arr2[$i] arr3[$i]=$arr3[$i] ....\n";

To me, the above line is clear, unambiguous and requires zero contortions to 
either write or read (by the coder). I have been so far unable to write in 
python anything that comes anywhere within even shooting distance (with an 
ICBM) of this (but I'd love to be proven wrong ;)

I appreciate your solutions, but they all require the building of artificial 
structures or many temp variables. This makes for an ugly mess of the code if 
I have say 15 arrays for which I need to generate output like the above, and 
what annoys me is that a single well-interpolated line would do it (if such a 
facility existed in our otherwise beloved snake).

Oh well, I guess I'll just write the ugly mess.

Thanks for the help though.

Cheers,

f.