What's the difference between the pass statement:
def function(): pass and 3 dots:
def function(): ... Which way is better and faster to execute(CPython)?
2 Answers
pass has been in the language for a very long time and is just a no-op. It is designed to explicitly do nothing.
... is a token having the singleton value Ellipsis, similar to how None is a singleton value. Putting ... as your method body has the same effect as for example:
def foo(): 1 The ... can be interpreted as a sentinel value where it makes sense from an API-design standpoint, e.g. if you overwrite __getitem__ to do something special if Ellipsis are passed, and then giving foo[...] special meaning. It is not specifically meant as a replacement for no-op stubs, though I have seen it being used that way and it doesn't hurt either
1 Comment
mahoriR
One important thing to note is that - pass doesn't go well with typing and code editor will flag error when a function is supposed to return something but it just has a pass statement. On the other hand, same function with
... will not show any typing error.Not exactly an answer to your question, but perhaps a useful clarification. The pass statement should be use to indicate a block is doing nothing (a no-op). The ... (ellipsis) operator is actually a literal that can be used in different contexts.
An example of ellipsis usage would be with NumPy array indexing: a[..., 0]
...used where people want to indicate something they intend to fill in later (a 'todo' empty block) andpassto mean an block intended to have no code >>> A comment from stackoverflow.com/a/6189281/11890300...is a literal:type(...) <class 'ellipsis'>. It is just like doingdef f(): 5. So to your question:passEllipsis)... I'm not sure I want to stir the pot here and vote to reopen, but I at least added another link to cover the other thing being asked about (pass).