| From | To | Expression |
|---|---|---|
| 45 | "45" | str(data) |
| 45 | "101101" | bin(data) |
| 45 | "2D" | hex(data) |
| 45 | "\x00\x00\x00\x2d" | struct.pack('!i', data) |
| "45" | 45 | int(data) |
| "45" | "3435" | data.encode('hex') |
| "101101" | 45 | int(data, 2) |
| "2D" | 45 | int(data, 16) |
| "2D" | "\x2d" | binascii.unhexlify(data) or data.decode('hex') |
| "\x00\x00\x00\x2d" | 45 | struct.unpack('!i', data)[0] |
| "\x2d" | "2D" | binascii.hexlify(data) |
| "3435" | "45" | data.decode('hex') |
Comments are welcome here or in my original blog post regarding this table.
Definitely handy.
bin and hex add 0b and 0x to the beginning of the strings -- '{:b}'.format and '{:x}'.format don't do that.
encode('hex') and decode('hex') could use an explanation, and note that hex has been removed as an encoding in Python 3.
My fork with those changes: https://gist.github.com/agfor/5426355
Posted this on the blog too, but I realized I'd rather post here...
I forked this to compare it with Scala - https://gist.github.com/chris-martin/5426294 - but I'm not sure what to do with "\x00\x00\x00\x2d". What is this encoding (and why would you want it)?
With regards to encode / decode hex: In Python 3.2+, you can do codecs.encode(b"45", "hex_codec").
@chris-martin You would use it when you're dealing with binary encoded data. This gives deterministic positions of elements in structures relative to each other.
See here for more information.
Edit: To add to that, I saw on your site that you specialize in security. A clear application of binary encoding to infosec is shellcode!
I forked this to compare with Ruby (https://gist.github.com/havenwood/5426260), but I'm not sure what the "45" to "3435" conversion is meant to be?
@Caustic What I'm missing is the precisely what Python's str type really means. Do Python strings actually correspond directly to a specific representation as a bit array (rather than the more abstract notion of a unicode string that I'm used to on the JVM) - so "\x00\x00\x00\2d" doesn't strictly denote a 4-character string like I thought, but rather some 32 bits with no particular semantics attached?
@havenwood "4" is ascii 0x34, "5" is ascii 0x35. I don't know why you'd ever want to do this conversion.
ord('a') = 97
chr(97) = 'a'
@chris-martin Good point, I wouldn't. Except for just this. :P
Finished the Ruby translation, but gosh the "45" to "3435" and vice-versa are fugly.
@chris-martin In Python 2.x, str is basically a byte array. In Python 3.x, str is a Unicode string. We're looking at Python 2.x here, it seems.
@Niggler If you don't know what base it's in, you can specify a base of 0:
int('055', 0) -> 45 or int('0x55', 0) -> 85
I'm not sure what to do with "\x00\x00\x00\x2d". What is this encoding (and why would you want it)?
It's a 4-byte int in the network byte order.
@chris-martin, @havenwood to give you a real-world example for the hex encoding ("45" => "3435"): http://books.xmlschemata.org/relaxng/ch19-77143.html
this is quite inefficient, I know, but you sometimes need it for backwards compatibility.
oct(45) -> '055' and int('055', 8) -> 45