Why isn't my variable set when I call the other function?

Question

TypeError: '<' not supported between instances of 'NoneType' and 'int'

I have looked for an answer in Stack Overflow and found that I should be taking an int(input(prompt)), but that's what I am doing

def main():      
    while True:
            vPopSize = validinput("Population Size: ")
            if vPopSize < 4:
                print("Value too small, should be > 3")
                continue
            else:
                break

def validinput(prompt):
    while True:
        try:
            vPopSize = int(input(prompt))
        except ValueError:
            print("Invalid Entry - try again")
            continue
        else:
            break

You will need to add `return vPopSize` in the `def validinput(prompt):` — Taku, Apr 30 '17 at 16:19
The problem isn't the input. Python will implicitly `return None` from the valid input function. And there are two different `vPopSize` variables here — OneCricketeer, Apr 30 '17 at 16:21

score 47 · Answer 1 · answered Apr 02 '19 at 00:42

This problem also comes up when migrating to Python 3.

In Python 2 comparing an integer to None will "work," such that None is considered less than any integer, even negative ones:

>>> None > 1
False
>>> None < 1
True

In Python 3 such comparisons raise a TypeError:

>>> None > 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '>' not supported between instances of 'NoneType' and 'int'

>>> None < 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: '<' not supported between instances of 'NoneType' and 'int'

Copperfield · Answer 2 · 2017-04-30T17:46:26.987

you need to add a return in your function to get the number you input, otherwise it return an implicit None

def validinput(prompt):
    while True:
        try:
            return int(input(prompt)) 
            # there is no need to use another variable here, just return the conversion, 
            # if it fail it will try again because it is inside this infinite loop
        except ValueError:
            print("Invalid Entry - try again")


def main():      
    while True:
        vPopSize = validinput("Population Size: ")
        if vPopSize < 4:
            print("Value too small, should be > 3")
            continue
        else:
            break

or as noted in the comments, make validinput also check if it is an appropriate value

def validinput(prompt):
    while True:
        try:
            value = int(input(prompt)) 
            if value > 3:
                return value
            else:
                print("Value too small, should be > 3")
        except ValueError:
            print("Invalid Entry - try again")


def main():      
    vPopSize = validinput("Population Size: ")
    # do stuff with vPopSize

Thanks very much all!! I guess I lulled myself into thinking the return was implicit!! Daft really, but there you go... thanks again. — Dino3GL, Apr 30 '17 at 20:27

score 0 · Answer 3 · answered Dec 14 '21 at 17:14

Changing None value worked for me np.nan documentation

df_gpa.replace(to_replace=[None], value=np.nan, inplace=True)

code before

    def validate(self):
        df = self.df['column_name']
        print(df)
        for i in df:
            if i < 0:
                raise Exception(f"range is lower than 0.0: {i}")
            if i > 150:
                raise Exception(f"range is higher than 150: {i}")

code after

    def validate(self):
        df = self.df['column_name']
        df.replace(to_replace=[None], value=np.nan, inplace=True)
        print(df)
        for i in df:
            if i < 0:
                raise Exception(f"range is lower than 0.0: {i}")
            if i > 150:
                raise Exception(f"range is higher than 150: {i}")

score -2 · Answer 4 · edited Apr 30 '17 at 16:43

Try: 
    def validinput(prompt):
    print(prompt) # this one is new!!
    while True:
        try:
            vPopSize = int(input(prompt))
        except ValueError:
            print("Invalid Entry - try again")
            continue
        else:
            break

And you will notice when the function is called.

The problem is that validinput() does not return anything. You'd have to return vPopSize

score -5 · Answer 5 · answered Aug 19 '21 at 18:20

-5

should remove print() from the return of the function, so take the value and print it from outside

answered Aug 19 '21 at 18:20

Abd El Rahman

1

Why isn't my variable set when I call the other function?

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