[Numpy-tickets] [NumPy] #290: Some inconsistency in 'i' typecode

NumPy numpy-tickets at scipy.net
Sat Sep 23 13:51:52 CDT 2006


#290: Some inconsistency in 'i' typecode
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 Reporter:  faltet  |        Owner:  somebody
     Type:  defect  |       Status:  closed  
 Priority:  normal  |    Milestone:          
Component:  Other   |      Version:          
 Severity:  normal  |   Resolution:  invalid 
 Keywords:          |  
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Changes (by oliphant):

  * status:  new => closed
  * resolution:  => invalid

Comment:

 You are confusing equality testing on 2 different things: data-type object
 versus type objects that the data-types "wrap".

 Type-objects compare as equal only if they are the same type.  numpy.intc
 (the type object returned from dtype('i').type) and numpy.int_ (the type
 object returned from dtype('l').type) are two different type objects ---
 note that they both print the same however as numpy.int32 (on 32-bit
 platforms).  It can be a bit confusing, but it is intentional to shield
 the user from having to worry about it (I don't know why you keep worrying
 about it :-)).  While the type objects are technically different, they
 represent the same "data-type".  Therefore, it doesn't matter which one
 you use.

 The data-type equality testing tests for "equivalency" of types (not
 equality of type objects).  Therefore, dtype(numpy.intc) ==
 dtype(numpy.int_).  Also, data-type equality testing "converts" the object
 to a data-type object for convenience.

 So, my advice is to not use type-object equality testing.  Instead use
 dtype testing if you are trying to guarantee data-type compatibility.

-- 
Ticket URL: <http://projects.scipy.org/scipy/numpy/ticket/290>
NumPy <http://projects.scipy.org/scipy/numpy>
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