This should work for you:
import re
your_string = "reth10.890"
number = re.findall("\d+\.\d+", your_string)
requested_string = re.sub(number[0], '', a)
print(requested_string)
>>>'reth'
If your string contains more floats you have to select the last one in number
solved Need exctra last word in first line form below input [closed]