Write a Python program to check that a string contains only alphabets and numbers $($a$-$z$,$ A$-$Z and $0-9).$

The program should print True if the string only contains these characters and False if it contains any other characters.

input: "ABCDEFabcdef$123450"$

output: True

input: $"*$&$\%$@#$!\}\{"$

output: False

input: "asjgsdi$043^32"$

output: False