Re: python. was COMMON rates (was RE: Congrads John Earl!) -- MIDRANGE-L

Steve Richter wrote:

Hans can I ask you to explain this python code a little bit?

--------------------------------------------
# Set up the replacement variables
title = 'This is the title'
body = '<p>This is the body</p>'

# Write out the web page
print template % vars()
--------------------------------------------

What is "vars()"?  a collection of all the variables in the current
procedure?

Yes. More precisely, vars() is a built-in function that returns a dictionary of all the variables in the current scope.

A better way to code this would be to code a dictionary specifically for the replacement values to ensure separation between local variables and substitutions, but I thought using vars() would be easier to understand. That is, the better way to code it would be:

--------------------------------------------
# Set up the replacement variables
vars = {}
vars['title'] = 'This is the title'
vars['body'] = '<p>This is the body</p>'

# Write out the web page
print template % vars
--------------------------------------------

What is "%"? An argument seperator?

No, it is a string substitution operator. The first operand is a string containing % expressions which are substituted by elements of the right-hand operand. For example, "..%s.."%"abc" yields the string "..abc..".

The right-hand operand may be a list, in which case the substitutions go by position (much like sprintf() in C). For example, "%s%d" %('a',17) gives you "a17".

If a dictionary is coded as right-hand operand, the substitution variables in the left-hand string can be identified by name. For example, "%(m)s%(n)d" % {'m':'a', 'n':17} gives you "a17".


Is the "print" function able to retrieve the names of the variables and the
values also?

I'm not sure I understand the question. The above code takes advantage of the % operator, which is not specific to the print statement. The print statement simply takes a list of values.


If this is in the ballpark, can a programmer write a similar function that
receives a collection of variables as a parm?

I'm not quite sure what you're asking here too, and I suspect my answer will miss the point of your question. Python has two built-in collection classes (to simplify a little bit): lists and dictionaries. These, like any other objects in the language, can be passed freely to functions.

Does anything prevent python from running on the iSeries?

Ask Per Gummedal. Or try out his iSeries port at <http://home.no.net/pgummeda/>. I haven't tried it myself, so I can't comment personally on its quality. But the description at the web site seems reasonably up to date.


Thanks.  Python looks like it is fun, but using procs, the current RPG could
come close to your example like so:
  template = ReadSourceMemberIntoString( Srcf: SrcMbr ) ;
  AddToVarCollection( vars: 'Title': Title ) ;
  AddToVarCollection( vars: 'Body': Body ) ;
  ApplyVarsToTemplate( result, template, vars ) ;
  WriteToStdOut( result ) ;

Python is indeed a lot of fun!


And of course if RPG was open sourced, with IBM not losing any revenue
because it stays a part of websphere, then RPG could be extended in
experimental ways.  And the marketplace would decide if the extension is
worthwhile or not.

Steve Richter

I understand the rationale. But we'd probably need more people here to coordinate and validate the open-source changes to assure a reasonable level of quality.

Cheers! Hans