[Numpy-discussion] A couple more Numeric incompatibilities and a possible bug

Gary Ruben gazzar at email.com
Fri Mar 26 23:17:01 EST 2004

I found a couple more incompatibilities between Numeric and numarray object array handling.
When I print an object array in Numeric, if the __str__ method exists for the contained object type, Numeric uses it to print the object.
However, numarray uses the __repr__ method instead.
This breaks my doctest strings
I think Numeric does it correctly.

In my example I have a class called Err with
    def __repr__(self):
        return "Err(%s,%s,%s)" % (self.value, self.posErr, self.negErr)

    def __str__(self):
        return "%s +%s/-%s" % (self.value, self.posErr, self.negErr)

Numeric behaves as follows (Note: ArrayOfErr() is just building an object array):

>>> print ArrayOfErr([909., 802., 677., 585.], 1.0)
[909.0 +1.0/-1.0  802.0 +1.0/-1.0  677.0 +1.0/-1.0  585.0 +1.0/-1.0 ]

whereas numarray does this:

>>> print ArrayOfErr([909., 802., 677., 585.], 1.0)
[Err(909.0,1.0,1.0), Err(802.0,1.0,1.0), Err(677.0,1.0,1.0),

It also appears that if you try to apply the funtion abs to a built-in Python number type
after doing a 'from numarray import *',
instead of using Python's abs() function as Numeric does and returning a number, numarray
creates an ObjectArray containing the number and returns it. This may be a bug. Note also
the different answer when an int or float type is passed as an argument to cos:

>>> from Numeric import *
>>> cos(1)
>>> cos(1.)
>>> abs(-1)

>>> from numarray import *
>>> cos(1)
>>> cos(1.)
>>> abs(-1)
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