Thank you all. I agreed with Frank that > It would make sense to use the 'global' keyword if you have a module with various functions, several of which refer to 'foo', but only one of which changes the value of 'foo'.
I also found an example in cpython/lib/gettext.py, only 'textdomain function' can change '_current_domain', other functions just refer to it. So, it will be not evil or to use 'global' keyword correctly when there is only one function can change its value? Cameron Simpson <c...@cskk.id.au> 于2019年8月23日周五 下午3:15写道： > On 23Aug2019 09:07, Frank Millman <fr...@chagford.com> wrote: > >On 2019-08-23 8:43 AM, Windson Yang wrote: > >>In class.py > >> > >> class Example: > >> def __init__(self): > >> self.foo = 1 > >> def bar() > >> return self.foo + 1 > >> > >>Expect the syntax, why using class variable self.foo would be better (or > >>more common)? I think the 'global' here is relative, foo is global in > >>global.py and self.foo is global in Example class. If the global.py is > >>short and clean enough (didn't have a lot of other class), they are > pretty > >>much the same. Or I missed something? > >> > > > >One difference is that you could have many instances of Example, each > >with its own value of 'foo', whereas with a global 'foo' there can > >only be one value of 'foo' for the module. > > But that is an _instance_ attribute. Which is actually what Windson Yang > made. > > A class attribute is bound to the class, not an instance. The > terminology is important. > > Cheers, > Cameron Simpson <c...@cskk.id.au> > -- > https://mail.python.org/mailman/listinfo/python-list > -- https://mail.python.org/mailman/listinfo/python-list
