Forcing input from pre-defined list.

[scotty501]

Thank you both - brilliantly explained and actually made a lot of sense :)

I am starting (slowly) to get my head around coding, and you patience is appreciated.

On this the last statement, there is an error I believe as "first, second" is not defined?

first, second = validate('Enter first number: '), validate('Enter second number: ')
op = operation(f"Enter operation (one from: {', '.join(ops.keys())}): ")   # ensures that only defined operators are listed
print(f'Answer is {op(first, second)}')

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I solved the problem myself with some trial and error :)

It passes the pep8 approval too ;) Getting better for a newbie.

first = validate('Enter first number: ')
op = operation(f"Enter operation (one from: {', '.join(ops.keys())}): ")
second = validate('Enter second number: ')
print(f'Answer is {op(first, second)}')