I've been getting "NoneType object is not iterable" I have no idea why. I've checked my program a thousand times. Does anyone know how to fix this?

Question

I've been given out an assignment to write a program for a byteadder. The first program just checks if the entered number is valid or not and imports two other modules which are logicGates and fullAdder. logicGates has no errors, I am sure of it since it consists of gates ( if, else) and nothing more. Here's my code:

    dec1=int(input("Enter first decimal number: "))
    dec2=int(input("Enter second decimal number: "))

    def check(dec1,dec2):

        if (dec1+dec2)>255:
            print ("The decimal number you've entered is invalid. Please enter another number")
            dec1=int(input("Enter first number again: "))
            dec2=int(input("Enter second number again: "))
            return dec1,dec2

        elif (dec1+dec2)>+127 and (dec1+dec2)<-127:
            print ("The decimal number you've entered is invalid. Please enter your numbers again")
            dec1=int(input("Enter first number again: "))
            dec2=int(input("Enter second number again: "))
            return dec1,dec2

        else:
            print("Your number is now converted")
            return dec1,dec2

            print (check(dec1,dec2))

            import conversion
            lis1, lis2=conversion.bin2dec(dec1,dec2)

            import fullAdder
            add= fullAdder.fulladder(lis1,lis2)

            print (add)

And here's my fullAdder:

    import logicGates

    def fulladder(bin1,bin2):
        lis1=list(bin1)
        lis2=list(bin2)
        Cin=0
        lisEmp=[]

        for i in range(7,-1,-1):
            num1=int(lis1[i])
            num2=int(lis2[i])
            result1=logicGates.XOR(num1,num2)
            result2=logicGates.NAND(result1,Cin)
            result3=logicGates.OR(result1,Cin)
            Sum=logicGates.AND(result2,result3)
            result4=logicGates.AND(num1,num2)
            result5=logicGates.AND(result1,Cin)
            result6=logicGates.NOR(result4,result5)
            result7=logicGates.NOT(result6)

            Cin=result7
            lisEmp.insert(0,Sum)

        return lisEmp

Here's my code for bin2dec:

    def bin2dec(dec1,dec2):

        a=bin(dec1)
        b=bin(dec2)

        c=a[2:]
        d=b[2:]

        bin1=c.zfill(8)
        bin2=d.zfill(8)

        print (bin1)
        print (bin2)

This is the error I keep getting.

    Traceback (most recent call last):
      File "C:\Python34\main.py", line 26, in <module>
        lis1, lis2=conversion.bin2dec(dec1,dec2)
    TypeError: 'NoneType' object is not iterable

Your indentation is off. It impossible to say what your code does. — Klaus D., Jul 15 '17 at 17:34
check whether the conversion.bin2dec is returning any value first ? and provide the code for bin2dec — Sam Williams Jebaraj, Jul 15 '17 at 17:42
I've provided the code, Sir. Could you tell me what's wrong? @SamWilliamsJebaraj — Abírál Bháñdárí, Jul 15 '17 at 17:46
When I check out the following code: print (conversion.bin2dec(lis1,lis2)) This is the error I get: Traceback (most recent call last): File "C:\Python34\main.py", line 29, in add= fullAdder.fulladder(lis1,lis2) NameError: name 'lis1' is not defined — Abírál Bháñdárí, Jul 15 '17 at 17:48
In the future, a [mcve] should have the **shortest possible code** that produces the same problem. This program is much more complex than the shortest thing that creates the same error. — Charles Duffy, Jul 15 '17 at 18:20
return (bin1,bin2) at the end of the function will solve the problem. The function is not returning any value hence the error. — Sam Williams Jebaraj, Jul 15 '17 at 19:42
Possible duplicate of [Python Function Returning None](https://stackoverflow.com/questions/21471876/python-function-returning-none) — Foon, Jul 15 '17 at 22:32

Jonas Adler · Answer 1 · 2017-07-15T17:59:23.987

TLDR

The problem is that your function bin2dec does not have a return statement. You can fix it by adding

return bin1, bin2

to the end of bin2dec.

In depth explanation of the error

What actually happens, and why you get "NoneType object is not iterable", is that python does in fact not have multiple return values from a function, even if it looks like it. Instead, what happens is that a tuple is returned, and that this tuple is then unpacked.

So, what happens in your code is equivalent to this

result = conversion.bin2dec(dec1, dec2)
lis1, lis2 = result

Here, since you lack a return statement, we get that result is None, and then in the next line when lis1, lis2 = result is executed you try to unpack a None value, which is not possible and hence throws a TypeError.

score 0 · Answer 2 · answered Jul 15 '17 at 17:51

0

Your bin2dec function does not return values. It prints out values.

Try changing it to return bin1, bin2

answered Jul 15 '17 at 17:51

Anirudh Sridhar

183
1
12

williezh · Answer 3 · 2017-07-15T18:58:29.417

I think that code like this is better:

def input2num():
    while 1:
        dec1 = int(input("Enter first decimal number: "))
        dec2 = int(input("Enter second decimal number: "))
        if not -127 <= dec1+dec2 <= 127:
            print ("The decimal numbers you've entered is invalid."
                   " Please enter another two numbers.\n")
        else:
            print("Your number is now converted")                

            import conversion
            lst1, lst2 = conversion.bin2dec(dec1, dec2)

            import fullAdder
            add = fullAdder.fulladder(lst1, lst2)
            print(add)
            return dec1, dec2

dec1, dec2 = input2num()

fullAdder:

import logicGates

def fulladder(bin1, bin2):
    cin, lstEmp = 0, []
    for a, b in zip(bin1[::-1], bin2[::-1]): 
        num1, num2 = int(a), int(b)
        result1 = logicGates.XOR(num1, num2)
        result2 = logicGates.NAND(result1, cin)
        result3 = logicGates.OR(result1, cin)
        _sum = logicGates.AND(result2, result3)
        result4 = logicGates.AND(num1, num2)
        result5 = logicGates.AND(result1, cin)
        result6 = logicGates.NOR(result4, result5)
        result7 = logicGates.NOT(result6)
        cin = result7
        lstEmp.append(_sum)
    return lstEmp[::-1]

bin2dec:

def bin2dec(dec1, dec2):
    form = lambda x: bin(x)[2:].zfill(8)
    print(form(dec1), form(dec2))
    return form(dec1), form(dec2)

score 0 · Answer 4 · answered Jul 15 '17 at 19:41

def bin2dec(dec1,dec2):

        a=bin(dec1)
        b=bin(dec2)

        c=a[2:]
        d=b[2:]

        bin1=c.zfill(8)
        bin2=d.zfill(8)

        print (bin1)
        print (bin2)

There is no return statement in your function. Hence when it is called after execution it returns a None Value.

You can fix it by adding return(bin1,bin2) after the print

def bin2dec(dec1,dec2):

            a=bin(dec1)
            b=bin(dec2)

            c=a[2:]
            d=b[2:]

            bin1=c.zfill(8)
            bin2=d.zfill(8)

            print (bin1)
            print (bin2)
            return (bin1,bin2)

I've been getting "NoneType object is not iterable" I have no idea why. I've checked my program a thousand times. Does anyone know how to fix this?

4 Answers4

TLDR

In depth explanation of the error