[Python-Dev] operator.is*Type (original) (raw)

Thomas Heller theller at python.net
Wed Feb 22 13:03:55 CET 2006

Fuzzyman wrote:

Hello all,

Feel free to shoot this down, but a suggestion. The operator module defines two functions : isMappingType isSquenceType

These return a guesstimation as to whether an object passed in supports the mapping and sequence protocols. These protocols are loosely defined. Any object which has a _getitem_ method defined could support either protocol.

The docs contain clear warnings about that.

I suggest we either deprecate these functions as worthless, or we define the protocols slightly more clearly for user defined classes.

I have no problems deprecating them since I've never used one of these functions. If I want to know if something is a string I use isinstance(), for string-like objects I would use

try: obj + "" except TypeError:

and so on.

An object prima facie supports the mapping protocol if it defines a _getitem_ method, and a keys method. An object prima facie supports the sequence protocol if it defines a _getitem_ method, and not a keys method. As a result code which needs to be able to tell the difference can use these functions and can sensibly refer to the definition of the mapping and sequence protocols when documenting what sort of objects an API call can accept.

Thomas

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