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Variable not null python

Содержание
  1. How to Properly Check if a Variable is Not Null in Python
  2. 1. Check if the Variable is not null [Method 1]
  3. Syntax
  4. Example 1: Check String Variable
  5. Example 2: Check None Variable
  6. Example 3: Check Empty Variable
  7. 2. Check if the Variable is not null [Method 2]
  8. Syntax
  9. Example 1: Check String Variable
  10. Syntax
  11. Example 1: Check String Variable
  12. Related Tutorials:
  13. Recent Tutorials:
  14. None (null), или немного о типе NoneType
  15. Эквивалент null в Python: None
  16. Проверка на None
  17. Use try/except
  18. Use the non-equal operator
  19. Summary
  20. How To Check If A Variable Is Not Null in Python
  21. How to check type of any variable in python?
  22. To check if a variable is not Null
  23. Using “is not” or “ïs” keyword
  24. Using “==” and “!=” operator
  25. Using “if”, “if not” and else statement
  26. Summary

How to Properly Check if a Variable is Not Null in Python

To check if a Variable is not Null in Python, we can use 3 methods:

Note: Python programming uses None instead of null.

1. Check if the Variable is not null [Method 1]

The first method is using «is«, «not» and «None» keywords. Let’s see the syntax, Then the examples.

Syntax

Example 1: Check String Variable

The above program returns True if the variable is not null. If null, it returns False.

As you can see, in the output, the program returns True.

Example 2: Check None Variable

The program returned False because my_var is None (null).

Example 3: Check Empty Variable

We got True Because my_var is empty, not None

2. Check if the Variable is not null [Method 2]

The second method for checking if the variable is not null is using the != operator + None keyword.

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Syntax

Example 1: Check String Variable

The third method is the if condition. This method returns False if the variable is None or empty.

Syntax

Example 1: Check String Variable

This tutorial taught us how to check if the variable is not null. For more variable articles, check out:

Recent Tutorials:

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None (null), или немного о типе NoneType

Python 3 логотип

Ключевое слово null обычно используется во многих языках программирования, таких как Java, C++, C# и JavaScript. Это значение, которое присваивается переменной.

Концепция ключевого слова null в том, что она дает переменной нейтральное или «нулевое» поведение.

Эквивалент null в Python: None

Он был разработан таким образом, по двум причинам:

Многие утверждают, что слово null несколько эзотерично. Это не наиболее дружелюбное слово для новичков. Кроме того, None относится именно к требуемой функциональности — это ничего, и не имеет поведения.

Присвоить переменной значение None очень просто:

Существует много случаев, когда следует использовать None.

Часто вы хотите выполнить действие, которое может работать либо завершиться неудачно. Используя None, вы можете проверить успех действия. Вот пример:

    Python является объектно-ориентированным, и поэтому None - тоже объект, и имеет свой тип.

Проверка на None

Есть (формально) два способа проверить, на равенство None.

Один из способов — с помощью ключевого слова is.

Второй — с помощью == (но никогда не пользуйтесь вторым способом, и я попробую объяснить, почему).

Отлично, так они делают одно и то же! Однако, не совсем. Для встроенных типов - да. Но с пользовательскими классами вы должны быть осторожны. Python предоставляет возможность переопределения операторов сравнения в пользовательских классах. Таким образом, вы можете сравнить классы, например, MyObject == MyOtherObject.
 И получаем немного неожиданный результат:
Интересно, не правда ли? Вот поэтому нужно проверять на None с помощью ключевого слова is.

А ещё (для некоторых классов) вызов метода __eq__ может занимать много времени, и is будет просто-напросто быстрее.

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Check if a Variable is Not Null in Python

This Python tutorial help to check whether a variable is null or not in Python, Python programming uses None instead of null. I will try different methods to check whether a Python variable is null or not. The None is an object in Python.

This quick tutorial help to choose the best way to handle not null in your Python application. It’s a kind of placeholder when a variable is empty, or to mark default parameters that you haven’t supplied yet. The None indicates missing or default parameters.

  • The None is not 0.
  • The None is not as like False.
  • The None is not an empty string.
  • When you Comparing None to other values, This will always return False except None itself.

How To Check None is an Object

As earlier, I have stated that None is an Object. You can use the below code to define an object with None type and check what type is –

NoneObj = type(None)() print(NoneObj) //check print(NoneObj is None)

The above code will return the following output.

Option 1: Checking if the variable is not null

The following is the first option to check object is None using Python.

var = "hello adam" #check is not null if var is not None: print('Var is not null')

The output :
Var is not null

Option 2: Checking if the variable is not null

Let’s check whether a variable is null or not using if condition.

var = "hello adam" #check is not null if var: print('Var is not null')

Option 3: How To Check the Variable is not null

We can also check python variable is null or not using not equal operator–

test = "hello adam" # if variable is not null if test != None : print('Var is not null')

One thought to “Check if a Variable is Not Null in Python”

I loved reading this tutorial, on how to handle NULL by python.

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How To Check If A Variable Is Null In Python

Check if a variable is Null in Python

To check if a variable is Null in Python, there are some methods we have effectively tested: the is operator, Use try/except and the non-equal operator. Follow the article to better understand.

None and Null in Python

Nowaday, the keyword null is used in many programming languages to represent that the pointer is not pointing to any value. NULL is equivalent to 0. A newly created pointer points “miscellaneous” to a particular memory area. Assign the pointer to NULL to make sure it points to 0. Even though 0 is an invalid location, it’s easier to manage than when the pointer points to an area we don’t know.

In Python, there is no null but None .

None is a specific object indicating that the object is missing the presence of a value. The Python Null object is the singleton None .

In other words None in Python is similar to the Null keyword in other programming languages.

Check if a variable is Null in Python

Use the ‘is’ operator

The is operator is used to compare the memory addresses of two arguments. Everything in Python is an object, and each object has its memory address. The is operator checks if two variables refer to the same object in memory.

myVar = None # Check variable myVar is Null if myVar is None: print('The value of the variable myVar is None (null)')
The value of the variable myVar is None (null)

In the above example, I declared value = None and then used the is operator to check if value has None or not. If value is valid, then execute the if statement; otherwise execute the else statement.

Do not use the == operator to check for the value None . Because in some cases will lead to erroneous results.

Use try/except

Use try/except block to check if the variable is None .

The ‘if’ statement in ‘try’ to check variable ‘value’ exists and the value of ‘value’ is ‘none’

try: if myVar is None: print('The value of the variable myVar is None (null)') # Check name exists except NameError: print("The variable myVar does not exist")
The variable myVar does not exist

Use the non-equal operator

Another method to check if a variable is None is using the non-equal or != operator.

myVar = 1 if myVar != None: print('The variable is not null')

Summary

Here are ways to help you check if a variable is Null in Python. Or, if you have any questions about this topic, leave a comment below. I will answer your questions.

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My name is Jason Wilson, you can call me Jason. My major is information technology, and I am proficient in C++, Python, and Java. I hope my writings are useful to you while you study programming languages.

Name of the university: HHAU
Major: IT
Programming Languages: C++, Python, Java

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How To Check If A Variable Is Not Null in Python

Check if a variable is not Null

If you are having trouble with the “How to check if a variable is not Null in python” problem and don’t know how to do it, don’t miss our article. We will give you some solutions for checking if a variable is not Null. Read on it.

How to check type of any variable in python?

In Python, we can check the type of any variable by the following command:

integer = 1 print(type(integer))

To check if a variable is not Null

First, keep your mind that there is no “Null Type” in python, it is “None Type” instead. Now, let’s dive into our article to get some methods to verify whether a variable’s type is None or not

Using “is not” or “ïs” keyword

The result of this method is a boolean type. Look at the following example:

obj = 'This is a string' print(type(obj) is not None)
obj = 'This is a string' print(obj is None)

Using “==” and “!=” operator

The result of this method also is boolean type:

obj = 'This is a string' print(type(obj) == None)
obj = 'This is a string' print(obj != None)

Using “if”, “if not” and else statement

The last method to check if a variable is not Null is using if , if not and else statement.

obj1 = None obj2 = "String" if obj1: print("obj1 is not None") else: print("obj1 is None") if not obj1: print("obj2 is not None") else: print("obj2 is None")
obj1 is None obj2 is not None

Summary

To sum up, in Python, it is None type instead Null type and the condition to check if a variable is not Null is quite simple by using is , is not keyword, operator like != or == and if , if not , else statement.

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My name is Robert Collier. I graduated in IT at HUST university. My interest is learning programming languages; my strengths are Python, C, C++, and Machine Learning/Deep Learning/NLP. I will share all the knowledge I have through my articles. Hope you like them.

Name of the university: HUST
Major: IT
Programming Languages: Python, C, C++, Machine Learning/Deep Learning/NLP

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