[Numpy-discussion] immutable arrays

Travis Oliphant oliphant.travis at ieee.org
Wed Sep 20 13:18:19 CDT 2006

Martin Wiechert wrote:
> Hi list,
> I just stumbled accross NPY_WRITEABLE flag.
> Now I'd like to know if there are ways either from Python or C to make an 
> array temporarily immutable.
Just setting the flag


  make immutable:
  a.flags.writeable = False

  make mutable again:
  a.flags.writeable = True


  make immutable:
  a->flags &= ~NPY_WRITEABLE

  make mutable again:
  a->flags |= NPY_WRITEABLE

In C you can play with immutability all you want.  In Python you can 
only make something writeable if you either 1) own the data or 2) the 
object that owns the data is itself "writeable"


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