Need help with basic Python conditional statements

Question

Hi, everyone!

I would like to request some assistance with an activity that I'm tasked to complete (see below). I believe that I am simply not understanding independent if-else statements -- and how a line of code will execute if it meets (condition). Reading my textbook and trying various iterations of the same code is not helping me. Any assistances and/or other readable online resources would be much appreciated! Thanks much!

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user_num1 and user_num2 are read from input.

• If user_num1 is less than 0, output 'user_num1 is negative'.

• If user_num2 is greater than 14, assign user_num2 with 2.

• Otherwise, output 'user_num2 is less than or equal to 14'.

My work:

user_num1 = int(input())

user_num2 = int(input())

if user_num1 < 0:

print('user_num1 is negative')

if user_num2 > 14:

user_num_2 = 2

print('user_num2 is', user_num2)

else:

print('user_num2 is less than or equal to 14')

Answer 1

Hi Liz, the problem here is related to flow of Python conditional statements.

An else statement in python only executes code when the preceding if block evaluates to false.

If we look at the code you provided, this means python will print 'user_num2 is less than or equal to 14', any time if user_num2 > 14 evaluates to false.

This means that any time user_num2 is less than or equal to 14, user_num2 is less than or equal to 14 will be printed. The problem occurs because this statement will be printed when a negative number is inputted (user_num2<14). In this scenario, both `user_num1 is negative` and user_num2 is less than or equal to 14 will be printed.

To fix this issue, we can use the else if functionality. This will ensure that only one print statement will be executed:

user_num1 = int(input())

user_num2 = int(input())

if user_num1 < 0:

print('user_num1 is negative')

elif user_num2 > 14:

user_num_2 = 2

print('user_num2 is', user_num2)

else:

print('user_num2 is less than or equal to 14')

Once we replace the if with an else if, if use_num1 <0, we print ('user_num1 is negative') and then exit the branches. The last branch will be skipped and only user_num1 is negative will be printed.