A simple way but dangerous way to do this would be to use eval()
. eval()
executes the string passed to it as code. The dangerous thing about this is that if this string is gained from user input, they could maliciously execute code that could break the computer. I would get the input, check it with a regex, and then execute it if you determine if it's OK. If it's only going to be in the format "number operation number", then you could use a simple regex:
import re
s = raw_input('What is your math problem? ')
if re.findall('\d+? *?\+ *?\d+?', s):
print eval(s)
else:
print "Try entering a math problem"
Otherwise, you would have to come up with something a bit stricter than this. You could also do it conversely, using a regex to find if certain things are not in it, such as numbers and operations. Also you could check to see if the input contains certain commands.