> >> Which is preferred: > >> > >> for value in list: > >> if not value is another_value: > >> value.do_something() > >> break > > Do you really mean 'is' or '=='?
Let me expound on how 'is' and '==' are very different. It may work for some comparisons but often not for others. Certain examples work because of the Python implementation. >>> c = 1 >>> d = 1 >>> c is d # This only works because CPython caches small values. True >>> c == d True >>> a = 10000000000000 >>> b = 10000000000000 >>> a is b False >>> a == b True >>> 10000000000000 is 10000000000000 True '10000000000000 is 10000000000000' works because the interpreter caches the number because it is on the same line. Only use 'is' if you are looking for objects like True, False, None or something that MUST be exactly the same object. In general, use '=='. Ramit Ramit Prasad | JPMorgan Chase Investment Bank | Currencies Technology 712 Main Street | Houston, TX 77002 work phone: 713 - 216 - 5423 -- This email is confidential and subject to important disclaimers and conditions including on offers for the purchase or sale of securities, accuracy and completeness of information, viruses, confidentiality, legal privilege, and legal entity disclaimers, available at http://www.jpmorgan.com/pages/disclosures/email. -- http://mail.python.org/mailman/listinfo/python-list
