[Tutor] [Re:] I need help with the following question

[Oscar Benjamin]

On 10 September 2013 08:58, Thabile Rampa <thabilerampa at gmail.com> wrote:
> On Aug 27, 2013, at 3:40 AM, isaac Eric wrote
>
> <snip>
>
>> print "For a circle of radius %s the area is %s" % (radius,area)
> <snip>
>> Question: What is the purpose of %s ?
>
> I will admit that this is homework for me. However, this is more for my log
> book and not for marks.
>
> According to my understanding, the purpose of the %s is to turn the numbers,
> which the program has recognized as numbers, into strings, so that they fit
> in the print command without any syntax errors.
>
> Could you guide me in the right direction if it is completely off?

You are correct. '%s' is used to convert numbers (or other non-string
things) into strings so that they can be used in places where text is
required. In the particular case of the print command, this is done
automatically so printing a number directly works just fine:

>>> a = 123.0
>>> print a
123.0
>>> print 'The size is:', a
The size is: 123.0

The '%s' form though allows you to insert the string representation of
the number at the appropriate place in the string making it a bid
cleaner to read e.g.:

>>> radius = 4
>>> pi = 3.1412654
>>> area = pi * radius ** 2

This one:

>>> print 'For a circle of radius', radius, 'the area is', area
For a circle of radius 4 the area is 50.2602464

is equivalent to this one:

>>> print 'For a circle of radius %s the area is %s' % (radius, area)
For a circle of radius 4 the area is 50.2602464

If you just want to get the string representation of a number you can
just use the str() function:

>>> area
50.2602464
>>> str(area)
'50.2602464'


Oscar