[Tutor] reading 2nd line

[Magnus Lycka]

At 17:59 2003-01-27 +0530, Jayprasad J. Hegde wrote:
>  a question about file (). Has it been introduced from Python 2.3 onwards?

No, it's in 2.2 as well. It's really part of the type/class
unification. Now you can use type names as constructors.

 >>> int('5')
5
 >>> int(5)
5
 >>> float('5')
5.0
 >>> file('c:/autoexec.bat')
<open file 'c:/autoexec.bat', mode 'r' at 0x015C5D98>

You can also subclass types now:

 >>> class NonNegInt(int):
...     def __init__(self, val):
...             if int(val) < 0:
...                     raise ValueError, 'Negative value!'
...             super(int, self).__init__(val)
...
 >>> print NonNegInt(5)
5
 >>> print NonNegInt(-5)
Traceback (most recent call last):
   File "<interactive input>", line 1, in ?
   File "<interactive input>", line 4, in __init__
ValueError: Negative value!
 >>> print NonNegInt(0)
0
 >>> a = NonNegInt(5)
 >>> print '*' * a
*****


-- 
Magnus Lycka, Thinkware AB
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