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Home / Undefined Is Not Iterable (Cannot Read Property Symbol(Symbol.iterator))

Undefined Is Not Iterable (Cannot Read Property Symbol(Symbol.iterator))

Table Of Contents

  • Quick Video Fix
  • What is TypeError: 'NoneType' object is not iterable?
  • How to Fix the 'TypeError: 'NoneType' object is not iterable' Error
    • 1st Fix: Use the isinstance() Built-in Function
    • 2nd Prepare: Exception Handling
    • 3rd Fix: The blazon() Built-in Function
  • Forum Feedback
  • Conclusion
    • Related Posts:

In this mail service, we provide iii fixes for the TypeError: 'NoneType' object is not iterable Error.

The "TypeError: 'NoneType' object is not iterable" is an error message in Python programming language that when an operation or a office is practical to an object of inappropriate blazon, Python will throw out an error and stops the program from executing. This error message has 2 parts which are cleaved downward into the following:

  1. TypeError – the object representation of the blazon of error encountered or being thrown.
  2. 'NoneType' object is not iterable – the fault message to assistance developers amend understand the error.

Some people even utilise the error equally a joke!

Quick Video Fix

The YouTuber walks you through how to deal with the error:

What is TypeError: 'NoneType' object is not iterable?

In Python, the error message "TypeError: 'NoneType' object is non iterable" is caused by iterating or using loops on a None or nothing variable. Basically, in common practise, it is non allowed to loop through a non-array information. Take a look at this example code:

fruits = None

for fruit in fruits:

print(fruit)

In line 2, Python recognizes that we are trying to employ a loop on the variable fruits. It volition immediately throw the "TypeError: 'NoneType' object is not iterable" message because "fruits" is None or a null information. We cannot possibly loop through None or null; it is similar counting how many books you take merely really, y'all do non have any declared.

Here is a basic example of how to properly iterate an array:

fruits = ["Apple", "Banana", "Mango", "Grapes"]

for fruit in fruits:

impress(fruit)

As you can see in line 1, nosotros are declaring the variable fruits as an array of strings (fruits). This will give us the output without errors beneath because this time we are iterating an array and not a None.

Apple

Banana

Mango

Grapes

How to Fix the 'TypeError: 'NoneType' object is not iterable' Fault

Sometimes, it is inevitable that variables or functions return None or null, and we accidentally forcefulness to loop through them causing this error to be thrown. Yet, there are multiple ways to fix this type of error by using the post-obit methods:

1st Fix: Use the isinstance() Born Function

The isinstance() role will check if the object (starting time statement) is an case or a subclass of classinfo class (second argument). We can use this built-in part to check if we should or we should not loop through a variable. Take a expect at this code example:

fruits = None

if(isinstance(fruits, list)):

for fruit in fruits:

impress(fruit)

else:

impress("Fruits variable is not an array")

To avoid getting the error, you can follow these steps using the isinstance() built-in function:

  1. In line i, if you declare the variable fruits as None and therefore makes Python understand information technology is surely not an assortment.
  2. In line 2, use an if argument using the isinstance() role as an statement to check if variable fruits is an array. This time the isinstance(fruits, list) part volition render false making the statement to fail and will skip the for-loop fugitive the 'TypeError: 'NoneType' object is not iterable' and executes line half-dozen after the else statement giving the "Fruits variable is not an array" output.

Now we can continue to the next lawmaking execution and fully avoid the 'TypeError: 'NoneType' object is not iterable' fault message. The Python isinstance() built-in function is used in so many ways not but for this type of error handling.

2d Fix: Exception Handling

In Python, we can handle errors and exceptions like the 'TypeError' error using the endeavor except statement. Follow these steps for exception handling:

  1. Whatever errors and exceptions thrown inside the try argument will exist caught and will skip to the except argument execution. Look at the example code beneath:

fruits = None

try:

for fruit in fruits:

print(fruit)

except:

print("Fruits variable is not an array")

  1. In this case, the fruits variable is None and code line number 3 volition surely throw the 'TypeError: 'NoneType' object is not iterable' error; all the same, this will be caught and outputs "Fruits variable is not an array".

We have avoided the error once again using Python'due south exception handling.

third Gear up: The type() Congenital-in Office

But like the isinstance() function in the first fix which determines if the passed argument is an instance of a data type and returns a boolean value, the type() role returns the information type of the passed statement. This is very useful while you figure out the type of variable used in runtime.

fruits = None

if blazon(fruits) is list:

for fruit in fruits:

print(fruit)

else:

print("Fruits variable is not an array")

This time, follow these steps if you lot adopt to employ the type() born function:

  1. Check the datatype of the variable fruits and check if it is a listing type using the "is" operator.
  2. In the code above, the if-statement is false and will not execute the for-loop and jumps to the "else" part of the condition avoiding the TypeError to exist thrown by the system.

Wait at the comparing of the type() and isintance function in Python.

Forum Feedback

To sympathize more nearly TypeError: NoneType object is not iterable, and the problems users have with it, we looked through several Python forums. In general, users are interested in TypeError: NoneType object is not iterable Python, TypeError: NoneType object is non iterable list, and TypeError: NoneType object is non iterable matplotlib.

They also wanted to know more than about TypeError: NoneType object is non iterable tensorflow and TypeError: NoneType object is not iterable empire.

TypeError NoneType object is not iterable in Python

A Python novice started working on a code for a school projection, and he couldn't figure out why he was getting the TypeError: 'NoneType' object is non iterable.

  • He asked the Python community, which was very helpful in solving the problem.
  • They explained to him that the most likely scenario was that he had missed the render statement in his method.
  • Since the method was returning "None," and "None" was iterable, he was getting the error.
  • However, the user added that it was a difficult error to spot for novices considering of all the involved variables and warned that it might accept y'all a while to figure it out.

A poster explains that NoneType is a type of None object or in other words, an object which has no value.

  • The person specifies that lists accept _iter_ method, which allows iteration. But since you tin't iterate over objects that are None, you get an mistake.
  • He adds that objects should be checked for nullity with the following code – if obj is None: or if obj is not None: to avert mistakes.
  • The person also said that novices find it difficult to grasp the concept and often forget to prepare the return value.

Some other computer expert said that making a typing mistake somewhere in the code might result in a NoneType object is non iterable. He advises that you check the spelling carefully to make sure that y'all're doing everything as suggested by the Python Style Guide.

NoneType object is not iterable when returning back the values Stack Overflow

A person remarks that you might go a TypeError: 'NoneType' object is non iterable due to many reasons. Nevertheless, one of the near common ones that new Python users do is that they iterate on numbers, while they should iterate on collections. To fix the issue, he says that you have to use one of these codes: for i in (number): or for i in 'number': and that yous take to recheck all lines of lawmaking carefully and change it accordingly.

Some other individual says that if you continue to get a NoneType mistake, you lot might have forgotten something equally simple equally quotation marks somewhere in a list you're trying to return. So, he advises that yous go over the lawmaking to observe the fault. The right version should look similar to this – ['word', 'discussion', 'word'], otherwise you'll continue getting the aforementioned mistake because information technology tin't notice the variable.

A computer user mentioned that he was trying to write a code to round-up grades, but he was getting a NoneType error in Python 3.x. He reached out the Python customs for aid, and they explained to him that his mistake was a uncomplicated ane. The user had used "impress" instead of "return," and as a result, his office didn't take annihilation to return.

Another person commented that TypeError: NoneType object is non iterable might be the result of a return statement indented incorrectly.

A forum poster shared that he was having some issues with matplotlib in Python 3.seven.0.

  • The program he wrote worked fine on some other device, but when he tried information technology on his computer, he got the NoneType object is not iterable mistake.
  • The user tried to switch from IDE to IDLE, reinstall matplotlib, and he even uninstalled Python and installed it again.
  • After consulting with other forum members, he discovered that matplotlib has a issues in the iii.0.0 version, which was causing the TypeError.
  • His options were to wait for the bug to exist fixed or downgrade his version of matplotlib.

A forum fellow member observed that he had checked his variables and that they were not None Type and that his plan was running correctly on the first time. Notwithstanding, when he attempted to run it a 2d fourth dimension, he kept getting NoneType object error. Other members of the Python customs explained to him that he had issues with the logic in his code and that he hadn't explicitly set a return.

Decision

To avoid getting the error 'TypeError: 'NoneType' object is not iterable', brand sure that you take all the weather in place that will return the information that yous need. Do non use loops on a None or null variable every bit it will return this mistake. Basically, Python will iterate an array when yous correctly declare the strings to be reported back.

For these suggested fixes, at that place are instances where the blazon() function is more applicable than the insintance() function in Python. The isintance() congenital-in function works with sub-classing while the type() congenital-in function will only return the blazon of object and render a comparison of the blazon of object of an object to exist true if you use the verbal same blazon object on both sides.

As you progress your programming experience, you will surely encounter hundreds, if non thousands, of this kind of fault. You lot tin can predict that a given variable is not an assortment to exist iterated or a role may return None then you could apply the fixes given above. This error is common when you are just starting to write code. Just, through time, dedication, and patience you volition become used to catching and preventing this blazon of mistake as you build your apps and software.

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Source: https://errorcodespro.com/typeerror-nonetype-object-is-not-iterable/