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You certainly can do this in python and often will need to when dealing with binary formats. The struct library is a great help for this. (https://docs.python.o

You certainly can do this in python and often will need to when dealing with binary formats. The struct library is a great help for this. (https://docs.python.org/2/library/struct.html https://docs.python.org/2/library/struct.html)

Walkman 10y ago
> This module performs conversions between Python values and C structs represented as Python strings. You can, but probably it's even slower than doing regular bit shifting operations (<<, >>, &, |, ^, ~)
- deathanatos 10y ago
  Where you can, you should use struct. For example, decoding a 32-bit integer in struct is faster than doing it manually: In [11]: %timeit hex(b[0] | (b[1] << 8) | (b[2] << 16) | (b[3] << 24)) The slowest run took 6.89 times longer than the fastest. This could mean that an intermediate result is being cached. 1000000 loops, best of 3: 715 ns per loop In [12]: %timeit hex(struct.unpack('<I', b)[0]) The slowest run took 8.77 times longer than the fastest. This could mean that an intermediate result is being cached. 1000000 loops, best of 3: 587 ns per loop The resulting code is also going to be cleaner, especially if you end up needing to unpack multiple members at once, which is common when parsing a binary file. The struct module is, I believe, written in C. (Pedantically, the struct module isn't; the C module _struct is hidden/private, but if you open the source for struct.py, you'll see it referenced.)
deathanatos 10y ago
The struct library is great for decoding binary file formats, but it has no facilities for sub-byte packing such as what the article talks about. But if you have a structure composed of little or big-ending encoded 8-/16-/32-/64-bit signed/unsigned integers in a file (quite common) … struct is amazing.