If you are using a 3*4 keypad, of course you bothered from 7 wires to deal with it.
By this library, you will be able to interface it by single wire connected to one analog pin.
the default network resistors is 5Ks for rows and 2Ks for columns.
you can change it and declare that in constructor.
pass analogRead value to function: char button_content(float analog), it will return character pressed in char data type.
NOTE!: don't use different resistors values in rows or columns.