python 中的回溯是什么？

Question

My code

largest = None
smallest = None

while True:
    num = input("Enter a number: ")
    if num == "done" : break

    try:
        fnum=int(num)


    except:
            print("Invalid input")

    if largest is None:
        largest=fnum

    elif fnum > largest:
          largest=fnum

    if smallest is None:
        smallest=fnum
    elif fnum<smallest:
            smallest=fnum


print("Maximum is", largest)
print("Minimum is", smallest)

The Traceback error:

Traceback (most recent call last): File "C:\Users\Marjia Priyaa\Desktop\Python\maximum.py", line 16, in largest=fnum NameError: name 'fnum' is not defined

Answer 1

Python's traceback is the order of things going wrong in your code. Typically the last line is what's relevant to your error. In this case you are trying to reference a variable fnum which is considered undeclared because it is out of scope (trying to use non-existent variable). Try setting fnum = 0 before the try statement.