extract alphanumeric characters from a stirng python code example
Example: all alphanumeric characters for python python
alpha_numeric = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
alpha_numeric = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"