LeftPad in Python

def leftPad(inputStr, paddedLength, ch='.'):
  if len(ch) != 1:
    raise Exception('Invalid Input')
  
  paddedLength = paddedLength - len(inputStr)
  return ch * paddedLength + inputStr 
  
print leftPad('1', 1)
print leftPad('2', 2)
print leftPad('3', 3)
print leftPad('4', 4)
print leftPad('5', 5)
print leftPad('hello', 7)
print leftPad("foo",  6)
print leftPad("foo", 3)
print leftPad("foobar", 3)
print leftPad("foo", 6, "?")