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FAQ: Control Flow - Boolean Operators: not

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This community-built FAQ covers the “Boolean Operators: not” exercise from the lesson “Control Flow”.

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FAQs on the exercise Boolean Operators: not

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Why are the terms in the prewritten code bracketed (e.g. “(gpa >= 2.0)”)? The code seems to work even without brackets. Is this a style thing?

Can someone tell me why this is returning as " Expected graduation_reqs() with gpa = 0.0 and credits = 0 to return “You do not meet either requirement to graduate!”?

statement_one = False

statement_two = True

def graduation_reqs(gpa, credits):
if (gpa >= 2.0) and (credits >= 120):
return “You meet the requirements to graduate!”
if not credits >= 120:
return “You do not have enough credits to graduate.”
if not gpa >=2.0 :
return “Your GPA is not high enough to graduate”
if (gpa < 2.0) and (credits < 120):
return “You do not meet either requirement to graduate!”

1 Like

Study your logic. It is testing for one condition and returning. Failing that it is testing the other condition and returning. Failing that it cannot possibly pass the last condition. Bring that conditional to above the other two.

a < m and b < n

then

a < m

b < n

So the code I wrote at first, because my thought when reading the exercise was “I don’t see why not is essential here when I can just use normal operators to describe everything” was:

def graduation_reqs(gpa, credits):
if (gpa >= 2.0) and (credits >= 120):
return “You meet the requirements to graduate!”
if (gpa >= 2.0) and (credits < 120):
return “You do not have enough credits to graduate.”
if (gpa <2.0) and (credits >= 120):
return “Your GPA is not high enough to graduate.”
if (gpa <2.0) and (credits < 120):
return “You do not meet either requirement to graduate!”

I was told that this solution is wrong, but is that because I didn’t use ‘not,’ or because the code would genuinely not work?

I guess my overall question is, after this lesson and exercise, I don’t understand why I would use ‘not.’

It is so much easier to read and evaluate Python code if it is properly posted as Python, a language to which indentations are integral. Thus posted, it is easy to follow, and can be copied and pasted for testing.

To do so, just use the </> icon that is in the middle of the menu bar that appears at the top of the text box you are typing in.

If you do so, could you also include a copy of the error message rejecting your code?

Since we’ve already determined there is only one path to graduate, why have two more checks? It’s only rubbing salt into the wound. If however the wish is to inform of what tripped them up, then it could be presented in a reverse fashion…

if gpa < 2:
    return "does not meet GPA requirement"
elif credits < 120:
    return "does not meet credit requirement"
else:
    return “You meet the requirements to graduate!”

what is the purpose of “not” boolean?

How would you code: If any character in the string s is something other that “A”, “C”, “T”, or “G”, return False; otherwise return True.

s = "ACCTGCCCQTTTTA .... 1 million characters.... AT"

There are probably dozens of ways to code it. Here’s one

def find_bad_char(s):
    for ch in s:
        if not ch in "ACGT":
            return False
    return True