That was me using the import within the class. I only did it due to my ignorance. I am not advanced enough to use it like that and know what I am doing, so as suggested I just moved all of my imports to the top.
Python Newbie..... On Thursday 06 October 2005 08:21 pm, Kent Johnson wrote: > Daniel Watkins wrote: > > Recently, there has been an example of someone importing modules within > > a class definition. eg: > > > > class Exemplar: > > import re > > ...use re... > > > > It seems obvious to me that this is incorrect, though more through > > training than actual observation on my part, and it should be: > > > > import re > > > > class Exemplar: > > ...use re... > > It's not really incorrect, it is legal syntax and it will do what you > expect. It is not idiomatic and in general it is simpler to just put all > the imports at the top. > > > However, someone (I don't recall who) said that there were occasions > > when it would be appropriate to import modules the former way. I was > > just wondering under what circumstances importing should be done this > > way? > > That was me. I nest imports quite frequently in Jython code where the first > import of a module is fairly expensive in time. Putting the import in the > function that needs it delays the import and perhaps the module won't be > imported at all. > > import is an executable statement. When it runs, the interpreter first > looks to see if the module has already been imported. If so, the existing > module is bound to the import name in the current namespace. If the module > has not yet been imported, it is loaded *and executed*, then bound to the > name in the current namespace. > > So if module A imports B which imports C and D, then importing A will also > load and execute B, C and D. If any of these are time-consuming you may > want to defer them. > > I found with my Jython programs that I could shorten start-up time quite a > bit by deferring some imports until they were needed. > > Another reason for the nested style of imports is to resolve problems with > circular imports. There are some subtle problems that can occur when A > imports B and B imports A. By nesting one of the imports you can defer it > and sometimes avoid the problem. In this case I think removing the circular > import is a much better solution - circular dependencies are evil! > > Kent > > > Cheers, > > Dan > > > > _______________________________________________ > > Tutor maillist - Tutor@python.org > > http://mail.python.org/mailman/listinfo/tutor > > _______________________________________________ > Tutor maillist - Tutor@python.org > http://mail.python.org/mailman/listinfo/tutor _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
