Help me solve this python code without $"$re$"$ or anything advanced. Beginner python code. Nothing too long either. Thank you! please! I need to write a code that finds the common word which is windows.

for example:

Windows$7$

Windows$8\mathrm{.}1$

Output:

Original strings:

Windows$7$

Windows$8\mathrm{.}1$

Common values of given strings:

Windows

Here is my code but I keep getting the "output set$()$:

def find$\_$common$\_$characters$($str$1,$ str$2)$:

$$ str$1=$ str$1.$lower$()$

$$ str$2=$ str$2.$lower$()$

$$ str$1\_$words $=$ str$1.$split$()$

$$ str$2\_$words $=$ str$2.$split$()$

$$ common $=$ set$($str$1\_$words$)$ & set$($str$2\_$words$)$

$$ return $($common$)$

str$1=$ "Windows$7"$

str$2=$ "Windows$8\mathrm{.}1"$

result $=$ find$\_$common$\_$characters$($str$1,$ str$2)$

print$("$Common Words:", result$)$

the output it keeps providing is this

Common Words: set$()$

I need the output to say "windows"

since the common word is windows