[Baypiggies] Discussion for newbies/beginner night talks

Paul McNett p at ulmcnett.com
Sat Feb 10 02:05:17 CET 2007

Dennis Reinhardt wrote:
> At 03:57 PM 2/9/2007, Shannon -jj Behrens wrote:
>> On 2/9/07, Dennis Reinhardt <DennisR at dair.com> wrote:
>>> This is an optimization and as such may not be the first approach to
>>> consider.  All of the code samples I showed used string appends such as
>>>         str  = ""
>>>          str += "string 1"
>>>          str +  "string 2"
>>>         ...
>> #) Use triple quoted strings, and use buffers.
> Triple quoted strings are often a poorer solution.
>    1) to avoid breaking up the indentation structure, triple quoted
>       strings must either have lots of extra white space or must be
>       defined globally.  If globally, subroutine level parameter
>       substitution is awkward.

I respectfully disagree. Take this example:

class MyBizobj(...):
	def getCustomerInfo(self, cust_id):
		sql = """
select customers.name as name,
        sum(invoices.amount) as amount_total,
        blah as blah
   from customers
   left join invoices
     on invoices.cust_id = customers.id
  where customers.id = ?"""
		self.cur.execute(sql, (cust_id,))

On one level, it is kind of ugly because I don't indent the lines to 
match the indentation of the code. On the other hand, it is easy to follow.

>    2) Parameter substitution is very awkward for long blocks of
>       text.

Again, I disagree.

> A common idiom I run up against is defining html in which the user may have 
> already entered a value.  So, one might find:
>          html += "<input type=text name=xyz value=%s>" % previous("xyz")
> and where it is understood that previous() reads the invoking URL for the 
> xyz= parameter value.
> Doing this in a long triple string is ugly.

You should use named arguments in string formatting. Such as:

html += """
<input type="text" name="%(field_name)s" value="%(field_value)s">
""" % locals()

Ok ok, this example is kind of ugly too, but it seems better when you 
actually have a block of html.

pkm ~ http://paulmcnett.com

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