import re

exceptions = [
	re.escape("log"),
	re.escape("sin"),
	re.escape("cos"),
	r"[+-]?\d*\.?\d+(?:e[+-]?\d+)?"
]

s = "(var1 * 1.3e4 + abc)/log(blabla+2E3)*1.2E+23"
r = r"\b(?!(?:" + "|".join(exceptions) + r")\b)\w+\b"

print re.sub(r, "1", s, 0, re.I)