Michael Yanowitz schreef:
> Is it possible to have a static variable in Python -
> a local variable in a function that retains its value.
>
> For example, suppose I have:
>
> def set_bit (bit_index, bit_value):
> static bits = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
> bits [bit_index] = bit_value
>
> print "\tBit Array:"
> int i
> while (i < len(bits):
> print bits[i],
> print '\n'
>
>
> I realize this can be implemented by making bits global, but can
> this be done by making it private only internal to set_bit()? I don't
> want bits to be reinitialized each time. It must retain the set values
> for the next time it is called.
You could do it by defining static_bits as a keyword parameter with a
default value:
>>> def set_bit(bit_index, bit_value, static_bits=[0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0]):
static_bits[bit_index] = bit_value
return static_bits
>>> set_bit(2, 1)
[0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
>>> set_bit(3, 1)
[0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
>>> set_bit(2, 0)
[0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
It might be a better idea to use a class for this though:
>>> class Bits(object):
def __init__(self):
self.bits = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
def set(self, index, value):
self.bits[index] = value
return self.bits
>>> bits = Bits()
>>> bits.set(2, 1)
[0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
>>> bits.set(3, 1)
[0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
>>> bits.set(2, 0)
[0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
When using a class, you can have different lists of bits independently
of each other in a program. And you can define other operations on the
bits: you could for example create methods to set or clear all bits at
once. With your approach, set_bit is the only function that has access
to the bits so you can't easily create other operations.
--
If I have been able to see further, it was only because I stood
on the shoulders of giants. -- Isaac Newton
Roel Schroeven
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