If you want to mainly base your code on the .NET framework, I’d highly recommend IronPython vs Python.NET. IronPython is pretty much native .NET – so it just works great when integrating with other .NET langauges. Python.NET is good if you want to just integrate one or two components from .NET into a standard python … Read more
I’m going to assume any readers of this question to have read both: Zero Piraeus’ answer and My explanation of CPython’s sets. The first thing to note is that hash randomization is decided on interpreter start-up. The hash of each letter will be the same for both sets, so the only thing that can matter … Read more
Yes, we can. But don’t do this at home. Seriously, the 1 object is used in many places and I have no clue what this might break and what that might do to your computer. I reject all responsibility. But I found it interesting to learn about these things. The id function gives us the … Read more
If you want to determine whether a value is exactly True (not just a true-like value), is there any reason to use if foo == True rather than if foo is True? If you want to make sure that foo really is a boolean and of value True, use the is operator. Otherwise, if the … Read more
All integers from -5 to 256 inclusive are cached as global objects sharing the same address with CPython, thus the is test passes. This artifact is explained in detail in http://www.laurentluce.com/posts/python-integer-objects-implementation/, and we could check the current source code in http://hg.python.org/cpython/file/tip/Objects/longobject.c. A specific structure is used to refer small integers and share them so access … Read more
TL;DR The actual speed difference is closer to 70% (or more) once a lot of the overhead is removed, for Python 2. Object creation is not at fault. Neither method creates a new object, as one-character strings are cached. The difference is unobvious, but is likely created from a greater number of checks on string … Read more
[*a] is internally doing the C equivalent of: Make a new, empty list Call newlist.extend(a) Returns list. So if you expand your test to: from sys import getsizeof for n in range(13): a = [None] * n l = [] l.extend(a) print(n, getsizeof(list(a)), getsizeof([x for x in a]), getsizeof([*a]), getsizeof(l)) Try it online! you’ll see … Read more
According to this thread: Indeed, CPython’s sets are implemented as something like dictionaries with dummy values (the keys being the members of the set), with some optimization(s) that exploit this lack of values So basically a set uses a hashtable as its underlying data structure. This explains the O(1) membership checking, since looking up an … Read more
A comment in the Python source code for float objects acknowledges that: Comparison is pretty much a nightmare This is especially true when comparing a float to an integer, because, unlike floats, integers in Python can be arbitrarily large and are always exact. Trying to cast the integer to a float might lose precision and … Read more
So what is CPython? CPython is the original Python implementation. It is the implementation you download from Python.org. People call it CPython to distinguish it from other, later, Python implementations, and to distinguish the implementation of the language engine from the Python programming language itself. The latter part is where your confusion comes from; you … Read more