how to check if number input is empty, using a if statement

the title say it all, i tried doing this:

import random

speed = float(input("Which was the speed of the vehicle in that moment? "))

trafficTicket = 0

if speed == "": 

    print("The speed was not informed. ")

    randomNumber = random.randint(1, 120)

    RandomTrafficTicketValue = randomNumber * 7

    print(f"O value of the traffic ticket in this situation is going to be {RandomTrafficTicketValue} dollars. ")

if speed < 30:

    print("The vehicle's speed is very low, tell the driver to change hands. ")

if speed > 90:

    trafficTicketValue = speed - 90

    print(f"Due to speed above the permitted speed, the driver must receive a trafficTicket worth {trafficTicketValue * 7} dollars. ")

but got this error: ValueError: could not convert string to float: ''

Any way to go around it, so i can make a if statement when the user dont type anything?

i tried finding a solution based in what i needed but only found a question involving python made in 2010, and that dont are especially what im trying to find

>Solution :

Accept the input as a plain string and check if it is empty before you call float():

speed = input("what was your speed? ")

# if they actually typed something, convert it to a float
if speed:
    speed = float(speed)

    # now handle the various speed values

else:
    print("You did not enter anything")