Regex problem

Question

Hey, im trying to make a regular expression to Match a quadratic Polynom of the Form +-(any integer)x^2+-(any integer)x+-(any integer)
So far i got
import re
quadratic_polynom=r'-?\d*(x\^2)[\+-]?(\d*x)?[\+-]?\d*'
while True:
userinput=input(':')
if userinput == 'quit':
break
elif re.match(quadratic_polynom,userinput):
# Code....
But the Problem is, i cant get the regex to dont Match for Example x^2+ With a missing integer Or x

Answer 1

I only know about Perl standard regex and I hope it's similar to yours.
/(-?([1-9]\d*)?x\^2)([+-]([1-9]\d*)?x)?([+-]([1-9]\d*))?/
I'll try to explain how it works,
-? means we are not sure if there is a minus sign or not.
[1-9]\d* checks for one or more numbers.
x\^2 checks for x squared but ^ is escaped with a backslash.
The rest works the same but make sure you do (...)? because quadratic equations can just be 2x^2, they don't have to be 2x^2 + 3x + 5.

Answer 2

Edited my answer.
Yeah you enclose everything with a question mark because that can be absent in a quadratic equation.

Answer 3

Well Thank you for your answer, is the double paranthesis "([+-] (...))?" preventing The regex from matching for Example "x^2+" ? My regex Works good so far, but the m Problem was i couldnt get it to Miss Match expressions like that

Answer 4

I tried it, still doesnt work :/ yours also seem to dont Match x^2 without integers infront of it

Answer 5

Still doesnt work :/ maybe ruby is diffrent in this small Part. My only Problem is, that the regex matches "x^2+" or "x^2+x+", the rest Works fine

Answer 6

Its still not working :/