design of python: why is assert a statement and not a function? Question: In Python, assert is a statement, and not a function. Was this a deliberate decision? Are there any advantages to having assert be a statement (and reserved word) instead of a function? According to the docs, assert expression1, expression2 is expanded to …
Why are slice and range upper-bound exclusive? Question: I know that when I use range([start], stop[, step]) or slice([start], stop[, step]), the stop value is not included in the range or slice. But why does it work this way? Is it so that e.g. a range(0, x) or range(x) will contain x many elements? Is …
What's the difference between __builtin__ and __builtins__? Question: I was coding today and noticed something. If I open a new interpreter session (IDLE) and check what’s defined with the dir function I get this: $ python >>> dir() [‘__builtins__’, ‘__doc__’, ‘__name__’, ‘__package__’] >>> dir(__builtins__) [‘ArithmeticError’, ‘AssertionError’, ‘AttributeError’, ‘BaseException’, ‘BufferError’, ‘BytesWarning’, ‘DeprecationWarning’, ‘EOFError’, ‘Ellipsis’, ‘EnvironmentError’, ‘Exception’, …
Which classes cannot be subclassed? Question: Is there any rule about which built-in and standard library classes are not subclassable (“final”)? As of Python 3.3, here are a few examples: bool function operator.itemgetter slice I found a question which deals with the implementation of “final” classes, both in C and pure Python. I would like …
Why can't I add a tuple to a list with the '+' operator in Python? Question: Python not support adding a tuple to a list: >>> [1,2,3] + (4,5,6) Traceback (most recent call last): File “<stdin>”, line 1, in <module> TypeError: can only concatenate list (not “tuple”) to list What are the disadvantages for providing …
Why isn't __new__ in Python new-style classes a class method? Question: The Changelog for Python 2.2 (where new-style classes were introduced) says the following about the __new__ function: __new__ is a static method, not a class method. I initially thought it would have to be a class method, and that’s why I added the classmethod …
Why are slices in Python 3 still copies and not views? Question: As I only now noticed after commenting on this answer, slices in Python 3 return shallow copies of whatever they’re slicing rather than views. Why is this still the case? Even leaving aside numpy’s usage of views rather than copies for slicing, the …
Why does Python's itertools.permutations contain duplicates? (When the original list has duplicates) Question: It is universally agreed that a list of n distinct symbols has n! permutations. However, when the symbols are not distinct, the most common convention, in mathematics and elsewhere, seems to be to count only distinct permutations. Thus the permutations of the …
Why are there no sorted containers in Python's standard libraries? Question: Is there a Python design decision (PEP) that precludes a sorted container from being added to Python? (OrderedDict is not a sorted container since it is ordered by insertion order.) Asked By: Neil G || Source Answers: There is a heapq in the standard …
What blocks Ruby, Python to get Javascript V8 speed? Question: Are there any Ruby / Python features that are blocking implementation of optimizations (e.g. inline caching) V8 engine has? Python is co-developed by Google guys so it shouldn’t be blocked by software patents. Or this is rather matter of resources put into the V8 project …
