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

Raymond Hettinger python at rcn.com
Wed Feb 22 22🔞58 CET 2006

But given :

True True Instance w getitem <type 'instance'> True True NewStyle Instance w getitem <class '_main_.cng'> True True [] <class UserList.UserList at 0x00F11B70> True True {} <type 'instance'> (Last one is UserDict) I can't conceive of circumstances where this is useful without duck typing as well.

Yawn. Give it up. For user defined instances, these functions can only discriminate between the presence or absence of getitem. If you're trying to distinguish between sequences and mappings for instances, you're own your own with duck-typing. Since there is no mandatory mapping or sequence API, the operator module functions cannot add more checks without getting some false negatives (your original example is a case in point).

Use the function as-is and add your own isinstance checks for your own personal definition of what makes a mapping a mapping and what makes a sequence a sequence. Or better yet, stop designing APIs that require you to differentiate things that aren't really different ;-)

Raymond

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