Fast Python, Slow Python by Alex Gaynor

Transcript

1. Fast Python, Slow Python Alex Gaynor
2. About me • Core developer of Django, PyPy, CPython, etc. • Director of the Python Software Foundation • Work at Rackspace (Thanks!)
3. A talk about two things
4. What is performance?
5. Why do we care about performance?
6. Lies, damned lies, and benchmarks
7. Performance is specialization.
8. Systems performance
9. What is Python?
10. What Python Isn’t • Cython • C • Numba • RPython
11. Excuses time
12. Dynamic typing
13. You can monkey patch anything
14. Slow vs Harder to optimize
15. PyPy
16. $ python! >>> print 2! 2! $ pypy! >>>> print 2! 2!
17. Let’s make a deal
18. How can we specialize our code?
19. Let’s talk about C
20. struct Point {! double x;! double y;! double z;! };!
21. class Point(objet):! def __init__(self, x, y, z):! self.x = x! self.y = y! self.z = z!
22. point = {! "x": x,! "y": y,! "z": z,! }!
23. Dictionaries vs. Objects
24. std::unordered_map<std::string, double> point;! point["x"] = x;! point["y"] = y;! point["z"] = z;!
25. Why don’t we care?
26. if [hex, bytes, bytes_le, fields, int].count(None) != 4:! raise TypeError('need exactly one argument')!
27. if [hex, bytes, bytes_le, fields, int].count(None) != 4:! raise TypeError('need exactly one argument')!
28. if (! (hex is None) + (bytes is None) + (bytes_le is None) +! (fields is None) + (int is None)! ) != 4:! raise TypeError!
29. Python makes everything easier
30. Let’s talk about strings
31. char *data = malloc(1025);! while (true) {! size_t n = read(fd, data, 1024);! data[n] = '\0';! char *start = data;! while (start < data + n) {! if (isspace(*start)) {! break;! }! start++;! }! printf("%s\n", start);! }!
32. while True:! data = os.read(fd, 1024)! print data.lstrip()!
33. Zero Buffer
34. from zero_buffer import Buffer! ! b = Buffer.allocate(8192)! with open(path, "rb") as f:! b.read_from(f.fileno())! for part in b.view().split(b":"):! part.write_to(sys.stdout.fileno())! sys.stdout.write('\n')!
35. https://zero-buffer.readthedocs.org/ https://warehouse.python.org/project/zero_buffer/
36. A few more myths • Functions calls are really expensive • Using only builtin data types will make your code fast • Don’t write Python in the style of Java or C
37. One Python
38. I hate heuristics
39. Let’s take a lesson…
40. Thank you! Questions? https://speakerdeck.com/alex/