It’s a combination of Boyer-Moore and Horspool. You can view the C code here: Fast search/count implementation, based on a mix between Boyer-Moore and Horspool, with a few more bells and whistles on the top. For some more background, see: https://web.archive.org/web/20201107074620/http://effbot.org/zone/stringlib.htm. From the link above: When designing the new algorithm, I used the following constraints: … Read more
-1 is a reserved value at the C level of CPython which prevents hash functions from being able to produce a hash value of -1. As noted by DSM, the same is not true in IronPython and PyPy where hash(-1) != hash(-2). See this Quora answer: If you write a type in a C extension … Read more
This has only been tested on Windows: You can do the following: import os os.startfile(“C:/Users/TestFile.txt”, “print”) This will start the file, in its default opener, with the verb ‘print’, which will print to your default printer.Only requires the os module which comes with the standard library
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
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
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
Inside a function, the bytecode is: 2 0 SETUP_LOOP 20 (to 23) 3 LOAD_GLOBAL 0 (xrange) 6 LOAD_CONST 3 (100000000) 9 CALL_FUNCTION 1 12 GET_ITER >> 13 FOR_ITER 6 (to 22) 16 STORE_FAST 0 (i) 3 19 JUMP_ABSOLUTE 13 >> 22 POP_BLOCK >> 23 LOAD_CONST 0 (None) 26 RETURN_VALUE At the top level, the bytecode … Read more
When you call id({}), Python creates a dict and passes it to the id function. The id function takes its id (its memory location), and throws away the dict. The dict is destroyed. When you do it twice in quick succession (without any other dicts being created in the mean time), the dict Python creates … Read more