[Tutor] How to write the __str__ function

[Alan Gauld]

On 14/05/17 19:03, Sydney Shall wrote:

> The code that I have so far is as folows:
> 
>   def __str__(self):
>          return("\n"
>                 "               Output from __str__ of POCWP. "
>                 "\n"
>                 "\n After the first turnover, during the "
>                 "'Population Of Capitals Init' cycle,"
>                 "\n the productivities were raised from 1.0 "
>                 "\n to a specific Unit Constant Capital (UCC) "
>                 "for each specific capital: "
>                 "\n The input value for the mean of UCC "
>                 "was %7.5f" % (self.ucc),

Here endeth the first string

>                 "\n The fractional sigma (FractionalSTD)"
>                 " of UCC that was input was %7.5f " % (self.fractsigma_ucc))

And here the second. Returning two strings separated
by a comma makes it a tuple. Instead put the two values in a tuple at
the end of a single concatenated string.

And while at it make life easier for your self and use triple quotes:

def __str__(self):
    return """
               Output from __str__ of POCWP.

After the first turnover, during the
'Population Of Capitals Init' cycle,
the productivities were raised from 1.0
to a specific Unit Constant Capital (UCC)
for each specific capital:
 The input value for the mean of UCC was %7.5f
 The fractional sigma (FractionalSTD) of UCC that was input was %7.5f
""" % ( self.ucc, self.fractsigma_ucc)

Tweak the formatting to suit.

However, I'm not sure thats really a good use of __str__,
I might be tempted to make that an explicit method that's
called pprint()  - for pretty-print - or somesuch.
__str__() methods are usually a fairly cocise depiction
of the objects state that you can embed in a bigger string.

Maybe pprint() would look like

def pprint(self):
    return """
               Output from __str__ of POCWP.

After the first turnover, during the
'Population Of Capitals Init' cycle,
the productivities were raised from 1.0
to a specific Unit Constant Capital (UCC)
for each specific capital: %s""" % self

And __str__()

def __str__(self):
   return """
The input value for the mean of UCC was %7.5f
The fractional sigma (FractionalSTD) of UCC that was input was %7.5f """
% (self.ucc, self.fractsigma_ucc)

Thus pprint() uses str() to create the long version while str()
just gives the bare bones result.

Just a thought.

-- 
Alan G
Author of the Learn to Program web site
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