Question 305974 in Xcode Question posted in
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Xcode – Unusual behaviour of returning old variable value in Python3

I was trying to just add some ifs in the function to complete a task in edube.org, related to taking care of the exception or safe gaurd your problem. Below is my program

import math

def inputValueCheck():
    
    x = input("Enter x: ")
    print('1 ',x)
    number = True
    if x.isnumeric() is False:
        print('enter positive digits only')
        inputValueCheck()
    elif x.isnumeric() is True and int(x) < 0:
        print('enter positive digits only')
        inputValueCheck()
    else:
        print('2 ',x)
        #return x
    print('3 ',x)
    return x
    
    
x = float(inputValueCheck())
y = math.sqrt(x)

print("The square root of", x, "equals to", y)

1st time Input –
Enter x: aaa,
output
-1 aaa
enter positive digits only

2nd time Input –
Enter x: 12
output
print 1 12
print 2 12
print 3 12
print 3 aaa

Traceback (most recent call last): File "main.py", line 21, in

x = float(inputValueCheck()) ValueError: could not convert string to float: ‘aaa’

Why is this behaviour by Python? Why is the old value of x i.e. ‘aaa’ here getting returned every time and causing an exception? Can anyone please explain?

Tags:

2

Answers


  1. 0

    You are trying to run a function that:

    1. doesn’t return anything if the input data is invalid, and
    2. re run the same function that doesn’t return anything.

    Just return the function instead of trying to run it again from within the same function. Also you can avoid the extra if statement by using or like this:

    import math

def inputValueCheck():
    x = input("Enter x: ")
    number = True
    if x.isnumeric() is False or int(x) < 0:
        print('enter positive digits only')
        return inputValueCheck()
    else:
        return x

x = float(inputValueCheck())
y = math.sqrt(x)

print("The square root of", x, "equals to", y)

    Also, what is the Number = True for?

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  2. 0

    When doing a function without argument, it is more difficult to check the type of x, but if you don’t want to define a function inputValueCheck(x), you can always try to convert the variable to a float with an ‘expect ValueError’ if it does’nt work
    I also did’nt understand the usage of ‘number = True’ so I made a script where it is useful :

    import math

def inputValueCheck():    
    number = False
    while number == False:
        x = input("Enter x: ")
        try:
            x = float(x)
            if x > 0:
                print("x is a positive number")
                number = True
                return x
            else:
                print("x is not a positive number")
        except ValueError:
            print("x is not a number")

x = float(inputValueCheck()) y = math.sqrt(x)

print('The square root of', x, "equals to", y)

    But there can be many way to do it

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