How to use a colon properly in the following code (Python) [closed]

I am learning Python and was trying out a code but it gave an error. i was expecting it to ask for an input of the degree of celsius i want to convert to fahrenheit, and then it would either tell me the converted value or (if the given value is <-273.15) it will print a sentence saying that it is not possible. But the code wouldn't run and it gave an error instead. The error probably has something to do with the colon but i am not sure.

Code:-

def con(Celsius):
    Fahrenheit = (float(Celsius)*9)/5 + 32
    return Fahrenheit

Celsius = float(input("Enter the temperature in Celsius: ")

if Celsius <= -273.15:
    print("The temperature in Fahrenheit is "+ str(con(Celsius)))
else:
    print("The lowest possible temperature that physical matter can reach is -273.15C")

Error:-

File ".\Celsius2Fahrenheit2.py", line 7
    if Celsius <= -273.15:
                         ^
SyntaxError: invalid syntax

I will be glad if someone can guide me through this and help me fix the error.