On 28/08/12 10:26, Richard D. Moores wrote:
I've been going through Steven D'Aprano's pyprimes (<http://pypi.python.org/pypi/pyprimes/0.1.1a>) and have many questions. One is why begin a function name with an underscore. He has several functions that do this. Two are:
[...]
I'm stealing these for their usefulness. But why the underscores?
Single-underscore names are generally the convention for "private" functions, methods, classes, or other names. Here, "private" means: - the function depends on platform-specific features that may not always be available; - the function is experimental, and will become part of the public library some day, but not yet; - the author doesn't want to treat the function as a supported part of the library, but only as an internal detail; - the function is subject to change without notice; - it is an implementation detail, and may become obsolete if the implementation changes; - or all of the above. Think of a single leading underscore as the Python equivalent of those stickers you see on electrical equipment that say "No user-serviceable parts". If you mess with it, you void your warranty. Python will not stop you if you use call a library's private functions from your code, but you can't exactly rely on it. The library author makes no promise (implied or explicit) that single underscore _functions will work the way you expect, or still be there in the next version. There are a few exceptions. For example, the collections.namedtuple type uses single underscore methods as part of its *public* interface, to ensure that the namedtuple methods don't clash with the tuple's named fields. But that's quite unusual. Also, when you do "from module import *", Python will skip any single underscore names. -- Steven _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
