str and __setitem__

bearophileHUGS at lycos.com bearophileHUGS at lycos.com
Thu Jan 25 12:06:42 CET 2007


Peter Otten:
> >>> class mutable_str(object):...     def __init__(self, value):
> ...             self._value = value
> ...     def __setitem__(self, index, value):
> ...             self._value = self._value[:index] + value +
> self._value[index+1:]
> ...     def __str__(self):
> ...             return self._value
> ...>>> a = mutable_str("123")
> >>> a[1] = "x"
> >>> print a

For this purpose an array may be better, if you have to change it often
and print is only once in a while:

from array import array
a = array("c", "123")
a[1] = "x"
print a

The OP can also use a class, if some other methods are needed:

from array import array

class mutable_str(object):
    def __init__(self, value):
        self._value = array("c", value)
    def __setitem__(self, index, value):
        self._value[index] = value
    def __str__(self):
        return self._value.tostring() # this requires time

a = mutable_str("123")
a[1] = "x"
print a

Probably array.array can be subclassed too...

bye,
bearophile




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