import re
price='25.34-34.55'
test=re.compile(r'[1-9]\d*\.\d*|0\.\d*[1-9]|[1-9]\d*').findall(price)[0]
test2=re.compile(r'-[1-9]\d*\.\d*|-0\.\d*[1-9]|-[1-9]\d*').findall(price)[0]
i=float(test)
x=-float(test2)
r=(x+i)/2
print r

> import re
> re.findall(r'\d+', 'hello 42 I'm a 32 string 30')
['42', '32', '30']

> re.findall(r'\d+', "hello 42 I'm a 32 str12312ing 30")
['42', '32', '12312', '30']

> re.findall(r'\b\d+\b', "hello 42 I'm a 32 str12312ing 30")
['42', '32', '30']
> re.findall(r'\b\d+\b', "hello,42 I'm a 32 str12312ing 30")
['42', '32', '30']
> re.findall(r'\b\d+\b', "hello,42 I'm a 32 str 12312ing 30")
['42', '32', '30']