Solve in Python:
Having two standards for a keypad layout is inconvenient!  
Computer keypad's layout:  


 
Cell phone keypad's layout:  


Solve the horror of unstandartized keypads by providing a function that converts computer input to a number as if it was typed by a phone.

Example:  
"789" -> "123"

Notes:  
You get a string with numbers only
def computer_to_phone(numbers):
  return "".join([str({0:0, 1:7, 2:8, 3:9, 4:4, 5:5, 6:6, 7:1, 8:2, 9:3}[int(n)]) for n in numbers])