[Numpy-discussion] optional arguments to the array constructor

Philip Austin paustin at eos.ubc.ca
Tue Jul 6 18:43:49 CDT 2004


(for numpy v1.0 on Mandrake 10 i686)

As noted on p. 25 the array constructor takes up to 5 optional arguments

array(sequence=None, type=None, shape=None, copy=1, savespace=0,typecode=None)
(and raises an exception if both type and typecode are set).  

Is there any way to make an alias (copy=0) of an array without passing
keyword values?  That is, specifying the copy keyword alone works:

test=N.array((1., 3), "Float64", shape=(2,), copy=1, savespace=0)
a=N.array(test, copy=0)
a[1]=999
print test

>>> [   1.  999.]

But when intervening keywords are specified copy won't toggle:

test=N.array((1., 3))
a=N.array(sequence=test, type="Float64", shape=(2,), copy=0)
a[1]=999.
print test
>>> [ 1.  3.]

Which is also the behaviour I see when I drop the keywords:

test=N.array((1., 3))
a=N.array(test, "Float64", (2,), 0)
a[1]=999.
print test
>>> [ 1.  3.]

an additional puzzle is that adding the savespace parameter raises
the following exception:


>>> a=N.array(test, "Float64", (2,), 0,0)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/lib/python2.3/site-packages/numarray/numarraycore.py", line 312, in array
    type = getTypeObject(sequence, type, typecode) 
  File "/usr/lib/python2.3/site-packages/numarray/numarraycore.py", line 256, in getTypeObject
    rtype = _typeFromTypeAndTypecode(type, typecode)
  File "/usr/lib/python2.3/site-packages/numarray/numarraycore.py", line 243, in _typeFromTypeAndTypecode
    raise ValueError("Can't define both 'type' and 'typecode' for an array.")
ValueError: Can't define both 'type' and 'typecode' for an array.

Thanks for any insights -- Phil





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