Python index starts at 0. Any possibility to set index value as 1 for any terminal?-CodePudding

I am porting the Matlab code to Python. In Matlab, indices start at 1, but in python, they start at 0. Is there any way to set the first index as 1 through a command line flag?

It will be very useful for programming during index iteration.

CodePudding user response：

No, there's no way to do this. Python is a 0-indexed language. Guido Van Rossum (Python creator) explained his reasons behind selecting 0-indexing over 1-indexing in this blog post:

http://python-history.blogspot.com/2013/10/why-python-uses-0-based-indexing.html

CodePudding user response：

As far as Python is concerned, there cannot be changes in the Indexing part. It always starts with 0 (Zero) only and progresses onwards. Hope this helps you.

CodePudding user response：

Actually, starting from 0 is easier for all computer-related tasks - it is just that mathematical notation, as inherited by matlab starts at 1.

For compatibility and ease-to-port code, I think you could write some special cased classes that would modify the indexes in access-time, so that one won't have to worry about changing indexes at a first porting-pass (but I'd drop those and revert to 0-indexed structures in a second pass).

You would have to use those special-purposed data structures instead of the built-in lists and tuples - and, when moving to n-dimensional arrays, in numpy code, it might become simply to hard to be worth it to have the " 1" data structures working, as there are lots of corner cases with multi-dimensional indexes.

For plain lists though, you can have a displaced list by just re-writting the __getitem__, __setitem__ and __delitem__ methods.

class MatList(list):
 
   def __getitem__(self, index):
       return super().__getitem__(index - 1)
   def __setitem__(self, index, value):
       return super().__setitem__(index - 1, value)
   def __delitem__(self, index):
       return super().__delitem__(index - 1)

Add more methods as needed (.index for example, or .pop)

CodePudding user response：

Ah, after some research I found the solution. This is doable, but I don't recommend it. You can subclass list and then replace list with your new wrapper. Like this:

class ListWrapper(list):
    def __getitem__(self, index):
        return super().__getitem__(index-1)


list = ListWrapper

lst = ListWrapper([1, 2, 3])
print(lst[2])  # => 2

This is only part of the solution though. You'll need to add more methods to change the index as you use them. For example, you'll need to make wrappers for __setitem__() and __delitem__().

CodePudding user response：

i'm not aware of whether you can change that by default. But you can specify the starting and ending indexes for loops with range, enumerate, etc. e.g.

for i in range(1, end   1):