Metric Converter

number = float(input())
inputMetric = input()
outputMetric = input()

if inputMetric == "mm":
    if outputMetric == "cm":
        number /= 10
    else:
        number /= 1000
elif inputMetric == "cm":
    if outputMetric == "m":
        number /= 100
    else:
        number *= 10
else:
    if outputMetric == "cm":
        number *= 100
    else:
        number *= 1000

print(f"{number:.3f}")


РЕШЕНИЕ С ТЕРНАРЕН ОПЕРАТОР:

number = float(input())
inputMetric = input()
outputMetric = input()

if inputMetric == "mm":
    number /= 10 if outputMetric == "cm" else 1000
elif inputMetric == "cm":
    number *= 0.01 if outputMetric == "m" else 10
else:
    number *= 100 if outputMetric == "cm" else 1000

print(f"{number:.3f}")


ИЛИ:

number = float(input())
inputMetric = input()
outputMetric = input()

number *= ((0.1 if outputMetric == "cm" else 0.001) if inputMetric == "mm" else
           (0.01 if outputMetric == "m" else 10) if inputMetric == "cm" else
           (100 if outputMetric == "cm" else 1000))

print(f"{number:.3f}")