Filters And Argument Unpacking

"Williams, James P2" <[email protected]> Sat, 12 Dec 2015 23:24:17 +0000
Newsgroups gmane.comp.python.cheetah
Message-ID <[email protected]>
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I wrote a custom filter that accepts some additional keyword arguments.

   class MyFilter(Cheetah.Filters.Filter):
       def filter(self,val,goo=3DFalse,moo=3D42,**kw):
           if goo or moo:
               [...snip...]
           else:
               return super(MyFilter,self).filter(val,**kw)

   ...
   template=3DCheetah.Template.Template(file=3Df,searchList=3D[...],filter=
=3DMyFilter)
   ...

In my template, I'm trying to call the filter, but unpacking a dictionary t=
o provide the new keyword arguments.  This example assumes $koo is in the s=
earch list.

   #set $args=3D{
       "goo": True,
       "moo": 52
   }
   This is ${koo,**$args}-koo.

I get a SyntaxError when the template is filled, apparently complaining abo=
ut the filter call.  The template compiles to the following, more or less, =
the caret matching the one in the traceback.

   _v =3D VFFSL(SL,"koo",True)
   if _v is not None: write(_filter(_v,**VFFSL(SL,"args",True),rawExpr=3D..=
.))
                                                              ^
I think the problem is that dict unpacking has to be the last argument, but=
 the rawExpr follows it.  I can't find this syntax rule in the docs, but it=
 seems to hold in an interactive session.

Is there a way to do this?  I know I can add an optional dictionary to the =
filter, and not use unpacking.

Thanks.

Jim

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<div class=3D"WordSection1">
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">I wrote a custom filter that accepts some additional keyword =
arguments.<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp; class MyFilter(Cheetah.Filters.Filter):<o:p></o:=
p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;def filter(self,val,goo=
=3DFalse,moo=3D42,**kw):<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;=
if goo or moo:<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;=
&nbsp;&nbsp;&nbsp;&nbsp;[...snip...]<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;=
else:<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;=
&nbsp;&nbsp;&nbsp;&nbsp;return super(MyFilter,self).filter(val,**kw)<o:p></=
o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp; ...<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp; template=3DCheetah.Template.Template(file=3Df,se=
archList=3D[...],filter=3DMyFilter)<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp; ...<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">In my template, I&#8217;m trying to call the filter, but unpa=
cking a dictionary to provide the new keyword arguments.&nbsp; This example=
 assumes $koo is in the search list.<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp; #set $args=3D{<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &#8220;goo&#8221;: True,=
<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &#8220;moo&#8221;: 52<o:=
p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp; }<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp; This is ${koo,**$args}-koo.<o:p></o:p></span></p=
>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">I get a SyntaxError when the template is filled, apparently c=
omplaining about the filter call.&nbsp; The template compiles to the follow=
ing, more or less, the caret matching the one in the
 traceback.<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp; _v =3D VFFSL(SL,&#8221;koo&#8221;,True)<o:p></o:=
p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp; if _v is not None: write(_filter(_v,**VFFSL(SL,&=
#8221;args&#8221;,True),rawExpr=3D...))<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbs=
p;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&=
nbsp; ^<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">I think the problem is that dict unpacking has to be the last=
 argument, but the rawExpr follows it.&nbsp; I can&#8217;t find this syntax=
 rule in the docs, but it seems to hold in an interactive
 session.<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">Is there a way to do this?&nbsp; I know I can add an optional=
 dictionary to the filter, and not use unpacking.<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">Thanks.<o:p></o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060"><o:p>&nbsp;</o:p></span></p>
<p class=3D"MsoNormal"><span style=3D"font-family:&quot;Courier New&quot;;c=
olor:#002060">Jim<o:p></o:p></span></p>
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