> -----Original Message----- > From: Tutor [mailto:tutor-bounces+crk=godblessthe...@python.org] On > Behalf Of Steven D'Aprano > Sent: Wednesday, August 12, 2015 6:43 AM > To: tutor@python.org > Subject: Re: [Tutor] a few question about my evolving program > > On Tue, Aug 11, 2015 at 08:23:00PM -0700, Clayton Kirkwood wrote: > > > Question 2: > > My current code: > > See "Look here" below. > > > There's an art to picking good variable names, neither too short nor too long, > just descriptive enough without being too verbose. > > Or to put it another way... > > The existence of a systematic application of knowledge or skill in effecting a > desired result in such a way as to be in accordance with the actual state of > reality is a factual statement when applied to the technique of making a > agreeable selection between hypothetical candidate appellations for > variables. > > *wink* > > I'm afraid that reading your code gives me a headache. You have > master_directory_file_list (which is a dict, not a list) and directory_file_list; > also target_filename_size (a dict, not a size), current_directory_path, > target_directory, current_file_list, file_list, and file_file_path_list, although I > admit that my head is spinning at the moment and that last one might be > inaccurate :-) > > I don't know how you can keep track of all those so-very-similar variable > names, especially since some of them lie about what they are! > (Claiming to be a list when they are actually dicts, etc.) Better names will > help. > > It is rare that stating what *type* a variable is will be helpful. E.g. > you normally wouldn't say "count_int" or "width_float", rather "count" > and "width". > > You need to find a balance between variable names which are too generic > and non-descriptive, and those which are too verbose and detailed. That will > come with experience, and from reading other people's code to see what > works and what doesn't work. > > It will also help if you can break your code up into small, self-contained > functions which can be digested by the reader in isolation. For example, if I > were writing your code, I might do something like this: > > > def name_is_seen_before(filename, already_seen): > """Returns whether or not filename has already been seen. > > If the filename has not been seen before, it is added to the > set of already seen filenames, and False is returned; otherwise > True is returned. > """ > if filename in already_seen: > return True > already_seen.add(filename) > return False > > > Then use it something like this: > > already_seen = set() > duplicates = set() > for name in bunch_of_names: > if name_is_seen_before(name, already_seen): > duplicates.add(name) > > > Obviously you have to get the bunch_of_names somehow first. To do that, > you can also simplify the process of iterating over files with a filter that > discards the files you don't care about: > > def is_media_file(filename): > extensions = ['jpg', 'gif', 'png'] # etc. > base, ext = os.path.splitext(filename) > return ext[1:].lower() in extensions > > def filter_media(filenames): > media_files = [] > for name in filenames: > if is_media_file(name): > media_files.append(name) > return media_files > > > The advantage of this is that you can write these small functions > independently of the rest of your loop, you can test them easily and satisfy > yourself that they work correctly, and then forget all the internal details of > how they work when you go to use them: > > > for dir_path, directories, filenames in os.walk(main_dir): > filenames = filter_media(filenames) > # ... continue processing ... > > > And you don't need to care that variable names are duplicated in different > functions, because each function is self-contained. There's no confusion > between variable "name" in one function and "name" in another, so there's > no need to try to come up with distinctive names for them both. > > The point being, the *details* of how the media files are filtered are not > important. You can "look inside" the filter_media() function when you care > about the details, and when you don't, you can just treat it as a black-box > that takes a list of file names and returns only those which are media files. > > Try redesigning your code to be a bit more hierarchical in this way, and see if > that makes it easier for you to solve the problem.
Thanks for the advice. I had much shorter names but, while still learning and comparing two files from perhaps different directories, it was less confusing for me to spell it out. Be patient, I am still learning, one step at a time. I'm sure you don't remember previous code, but I have finally been able to get rid of parentheses in for and if statements. It goes against everything that I used to do. I have already rewritten sections of code as I have become more experienced. So I am getting there.... Crk > > > > -- > Steve > _______________________________________________ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > https://mail.python.org/mailman/listinfo/tutor _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
