print - parameters ?

[Peter Abel]

Helmut Jarausch <jarausch at igpm.rwth-aachen.de> wrote in message news:<2sf68hF1jj1mlU1 at uni-berlin.de>...
> Hi,
> sorry for this probably very simple question.
> 
> How can I build a parameter list for 'print' ?
> 
> Background:
> I'd like to write a function like
> 
> def myprint(Msg,*Args) :
>    print (Msg,)+Args
> 
> when called as
> 
> myprint(MyMsg,x)
> 
> it should be equivalent to
> 
> print  MyMsg,x
> 
> but, e.g.
> 
> class ABC :
> 	def __str__(self) :
> 		return "ABC-class"
> 
> x=ABC()
> 
> myprint('this is',x)
> 
> gives
> 
> ('this is', <__main__.ABC instance at 0x4084fc8c>)
> 
> instead of
> 
> this is ABC-class
> 
> What am I missing (what sort of thing is the parameter list of print) ?
> Many thanks for a hint,
> 
> 
> Helmut Jarausch
> 
> Lehrstuhl fuer Numerische Mathematik
> RWTH - Aachen University
> D 52056 Aachen, Germany

As Alex pointed out there is a tiny difference 
between __repr__ and __str__ but with an eminent effect
see the following examples:

case 1:
-------
>>> class ABC:
... 	def __str__(self):
... 		return "ABC-class"
... 
>>> x=ABC()
>>> x
<__main__.ABC instance at 0x00DFA640>
>>> '%s' % x
'ABC-class'
>>> '%r' % x
'<__main__.ABC instance at 0x00DFA640>'


case 2:
-------
>>> class ABC:
... 	def __repr__(self):
... 		return "ABC-class"
... 	def __str__(self):
... 		return "ABC-class"
... 
>>> x=ABC()
>>> x
ABC-class
>>> '%r' % x
'ABC-class'
>>> 


So for both cases the following function works:

>>> def myprint(Msg,*Args) :
... 	format=''.join(['%s']*(len(Args)+1))
... 	print format % tuple([Msg]+map(str,Args))
... 

>>> class ABC:
... 	def __str__(self):
... 		return "ABC-class"
... 
>>> x=ABC()
>>> myprint('this is ',x)
this is ABC-class

>>> class ABC:
... 	def __repr__(self):
... 		return "ABC-class"
... 	def __str__(self):
... 		return "ABC-class"
... 
>>> x=ABC()
>>> myprint('this is ',x)
this is ABC-class
>>> 

BTW the need of the statement

... 	print format % tuple([Msg]+map(str,Args))

was new for me too.

Regards
Peter