Python: Ternary operator

Look at the definition of the function that returns the modulus of the number passed:

def abs(number):
    if number >= 0:
        return number
    return -number

But you can write it more succinctly. To do this, there must be an expression to the right of return, but if is an instruction, not an expression. In Python there is a construction that works like if-else but is considered an expression. It is called the tern operator - the only operator in Python that requires three operands:

def abs(number):
    return number if number >= 0 else -number

The general pattern looks like this: ` if else '.

Let's rewrite the initial version of get_type_of_sentence() in the same way.

It was :

def get_type_of_sentence(sentence):
    last_char = sentence[-1]
    if last_char == '?':
        return 'question'
    return 'normal'

Became:

def get_type_of_sentence(sentence):
    last_char = sentence[-1]
    return 'question' if last_char == '?' else 'normal'

print(get_type_of_sentence('Hodor'))   # => normal
print(get_type_of_sentence('Hodor?'))  # => question

You can put a ternary operator into a ternary operator. But you shouldn't do it that way because such code is hard to read and debug.

Instructions

Implement a function flip_flop() that takes a string as input and, if that string is 'flip', returns the string 'flop'. Otherwise, the function should return 'flip'.

Examples of calls:

print(flip_flop('flip'))  # => 'flop'
print(flip_flop('flop'))  # => 'flip'

Try writing two versions of the function: with the usual if-else, and with the ternary operator.

Definitions

• Ternary operator a way to turn a simple conditional instruction into an expression, such as number if number >= 0 else -number.