条件表达式无法正常运行（Python）

Question

I am supposed to write a few lines of code to create a conditional expression (ternary operation) that evaluates to string "negative" if user_val is less than 0 and "non-negative" if 0 or greater than 0.

The code I currently have prints "negative" when the number is less than zero but when a number 0 or greater is assigned to user_val it doesn't print "non-negative."

user_val = -9

cond_str = 'negative' 
cond_str if (user_val < 0) else
cond_str == 'non-negative'

print(user_val, 'is', cond_str)

I tried defining cond_str as an empty string and I also tried swapping around the statements so that cond_str=='non-negative' would go first. I also tried removing the second line of the code all together but it's still not working. Thanks for your help with this. Any advice or suggestions would be very much appreciated!

Answer 1

I think you mean to use:

cond_str = 'negative' if (user_val < 0) else 'non-negative'

The ternary operator must be on a single line, since Python is white-space sensitive.

Answer 2

I don't understand why you test an equality in the last statement.

For me the easiest is the following:

cond_str = 'negative' if user_val < 0 else 'non-negative'

You can chain an if statement with an assignation in Python to test which value you want to assign. This is called « ternary operator ».

Answer 3

Youll want to build a conditional statement to do this in one line. So: conditionalstatement = (userval >=0)? "non-negative" : "negative"; this way the 0 is registered as a non-negative. a simple program that you could expand on by using index or array.