Script to compress linear sequences of numbers as a strings with repeating sections taking the form: start:width:stop

sequence_compress.py

import numpy as np

def findSequence(x, delta_x, start=0):
	string = ""
	if len(x) == 1: return str(x[0]) + ','
	if len(x) == 2: return str(x[0]) + ',' + str(x[1]) + ','
	
	while (start<delta_x.size-1):
		
		end = start+1

		while(end < delta_x.size-1 and delta_x[end] == delta_x[end+1]):
			end+=1

		if end-start > 2:
			compressed = str(x[start]) + ":" + str(delta_x[end]) + ":" + str(x[end]) + ","
		else:
			compressed = str(x[start]) + ',' + str(x[end]) + ","
	
		string += compressed
		start=end+1

	return string

def xfrange(start, step, stop):
	if start<stop:
	  while start <= stop:
	      yield start
	      start += step
	else:
	  while start >= stop:
	    yield start
	    start += step

def uncompress(string):
	tokens = string.split(',')[:-1]

	x= []
	for token in tokens:
		subtokens = token.split(':')
		if len(subtokens) == 1:
			x.append(float(subtokens[0]))
		elif len(subtokens) == 3:
			subtokens = map(float, subtokens)
			for val in xfrange(*subtokens):
				x.append(val)

	return x

def computeDeltaX(x):
	delta_x = x[1:] - x[:-1]
	delta_x = np.concatenate(([0],delta_x))
	return delta_x


x = np.asarray([0.5,1,1.5,2,0.5,1,1.5,2,0.5,1,1.5,2,0.5,1,1.5,2])
delta_x = computeDeltaX(x)
string = findSequence(x, delta_x)
print uncompress(string)

x = np.asarray([0,1,2,3,4,5,6,7,8,9,10])
delta_x = computeDeltaX(x)
string = findSequence(x, delta_x)
print uncompress(string)

x = np.asarray([0,1,2,3,4,5,7,9,11,13,15,17])
delta_x = computeDeltaX(x)
string = findSequence(x, delta_x)
print uncompress(string)

x = np.asarray([5,4,3,2,1,0,-1,-2,-3,-4,-5])
delta_x = computeDeltaX(x)
string = findSequence(x, delta_x)
print uncompress(string)

x = np.asarray([5,10,3,7,8,4,1,2,3,4,5])
delta_x = computeDeltaX(x)
string = findSequence(x, delta_x)
print uncompress(string)

x = np.asarray([0])
delta_x = computeDeltaX(x)
string = findSequence(x, delta_x)
print uncompress(string)

x = np.asarray([0,1])
delta_x = computeDeltaX(x)
string = findSequence(x, delta_x)
print uncompress(string)