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Python.Engineering Wiki The Function Is Not Defined Javascript

The Function Is Not Defined Javascript

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Michael Zippo Michael Zippo 04.11.2021

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NameErrors are one of the most common types of Python errors. When you first start out, these mistakes can seem daunting. They are not too complicated. A NameError means that you tried to use a variable that does not yet exist.

In this guide, we are going to talk about the "NameError the name is not defined" error and the reason why it is high. We will look at some sample solutions for this error to help you understand how to resolve it in your code.

What is a NameError?

When trying a NameError is thrown using a name variable or invalid .

in Python, the code goes from top to bottom. This means that you cannot declare a variable after trying to use it in your code. Python doesn’t know what you wanted the variable to do

Most common NameError looks like this .

Let’s analyze some causes of this mistake.

cause n. 1: Incorrect variable or function name

It is easy for humans to overlook spelling mistakes. You can easily say what word should be, even if it is misspelled. Python does not have this capability.

Python cannot interpret names that you spelled correctly. This is because when you declare a variable or a function, Python stores the value with the exact name you declared

If there is a typo anywhere you try to refer to this variable, an error is returned

Consider the following code snippet:.

Our code returns:

to resolve this problem , all we need to do is correct, the " typing error ." If we use "printed (books)", our code returns:

If you get an error in the name, you must first make sure that you typed the variable or function name correctly.

cause # 2: call a function before the declaration

functions must be declared before being used, such as variables, because Python reads the Code from top to bottom.

write Let a program call a function before it is declared:

Our code returns:

We are trying to call print_books () in line three. However, we do not define this function later in our schedule . To correct this error, we can pass our function declaration to a place before using it:

Our code returns:

our code successfully printed the list of books

cause # 3:. remember to define a variable

As programs get bigger, it’s easy to forget to define a variable. If you do, a name error is thrown. This is because Python cannot work with variables until they are declared.

Let’s take a look at a program that prints a list of books:

Our code returns:

We have not declared a variable called "books". To solve this problem, we need to declare "books" before using it in our code:

Let try run our program again and to see what happens:

we defined a list of books, Python can print each book in the list

cause # 4: try printing a single word

To print a word in Python, you need to enclose it in single or double quotes. This tells Python that a word is a string. If a word is not in quotes, it is processed as part of a program. Consider the following () :

This code attempt print the word "books" to the console. The code returns an error:

Python treats "Books" as a variable name. To resolve this error, we can include the word "Books" in quotes:

Python now knows that we want to print a string to the console. Our new code returns:. Books

Cause n. 5: declaration of a variable of scope

There are two variable perimeters:. local and global

local variables are only accessible in the function or class in which they are declared. Global variables are accessible throughout the program.

Attempting to access a local variable outside the field in which it is defined will result in an error.

The following code should print a list of books followed by the number of books in the list:

our code returns:

Our code displays the list of books correctly. An error is returned in the last line of our code. Although we have declared the variable "books", we have only declared it within our print_books () function. This means that the variable is not accessible to the rest of our program

To solve this problem, we can declare the books in our main program, which will make them a global variable:

Our code returns:

our code prints all the books in the "books" list. our code prints the number of books in the list using len ().