How can I compress four floats into a string?

Question

I would like to represent four floats e.g, 123.545, 56.234, -4534.234, 544.64 using the set of characters [a..z, A..Z, 0..9] in the shortest way possible so I can encode the four floats and store them in a filename. What is the most efficient to do this?

I've looked at base64 encoding which doesn't actually compress the result. I also looked at a polyline encoding algorithm which uses characters like ) and { and I can't have that.

Answer 1

You could use the struct module to store them as binary 32-bit floats, and encode the result into base64. In Python 2:

>>> import struct, base64
>>> base64.urlsafe_b64encode(struct.pack("ffff", 123.545,56.234,-4534.234,544.64))
'Chf3Qp7vYELfsY3F9igIRA=='

The == padding can be removed and re-added for decoding such that the length of the base64 string is a multiple of 4. You will also want to use URL-safe base64 to avoid the / character.