[Tutor] how to tell if strings have numbers in them

[Brett]

I'm trying to get input and checking to see if it's a number.  x==int(x) 
works if it is a number, but causes an error if you input a string.  I made 
a list of 0-9 and tried for z in x/if z in list, and that seems to work, 
but its takes a lot of typing, is there an existing function that can check 
to see if a variable is a number?
When Schrodinger's cat's away,
the mice may or may not play,
no one can tell.