python assignment default value

Python Conditional Assignment

When you want to assign a value to a variable based on some condition, like if the condition is true then assign a value to the variable, else assign some other value to the variable, then you can use the conditional assignment operator.

In this tutorial, we will look at different ways to assign values to a variable based on some condition.

1. Using Ternary Operator

The ternary operator is very special operator in Python, it is used to assign a value to a variable based on some condition.

It goes like this:

Here, the value of variable will be value_if_true if the condition is true, else it will be value_if_false .

Let's see a code snippet to understand it better.

You can see we have conditionally assigned a value to variable c based on the condition a > b .

2. Using if-else statement

if-else statements are the core part of any programming language, they are used to execute a block of code based on some condition.

Using an if-else statement, we can assign a value to a variable based on the condition we provide.

Here is an example of replacing the above code snippet with the if-else statement.

3. Using Logical Short Circuit Evaluation

Logical short circuit evaluation is another way using which you can assign a value to a variable conditionally.

The format of logical short circuit evaluation is:

It looks similar to ternary operator, but it is not. Here the condition and value_if_true performs logical AND operation, if both are true then the value of variable will be value_if_true , or else it will be value_if_false .

Let's see an example:

But if we make condition True but value_if_true False (or 0 or None), then the value of variable will be value_if_false .

So, you can see that the value of c is 20 even though the condition a < b is True .

So, you should be careful while using logical short circuit evaluation.

While working with lists , we often need to check if a list is empty or not, and if it is empty then we need to assign some default value to it.

Let's see how we can do it using conditional assignment.

Here, we have assigned a default value to my_list if it is empty.

Assign a value to a variable conditionally based on the presence of an element in a list.

Now you know 3 different ways to assign a value to a variable conditionally. Any of these methods can be used to assign a value when there is a condition.

The cleanest and fastest way to conditional value assignment is the ternary operator .

if-else statement is recommended to use when you have to execute a block of code based on some condition.

Happy coding! 😊

Python Numerical Methods

This notebook contains an excerpt from the Python Programming and Numerical Methods - A Guide for Engineers and Scientists , the content is also available at Berkeley Python Numerical Methods .

The copyright of the book belongs to Elsevier. We also have this interactive book online for a better learning experience. The code is released under the MIT license . If you find this content useful, please consider supporting the work on Elsevier or Amazon !

< 2.0 Variables and Basic Data Structures | Contents | 2.2 Data Structure - Strings >

Variables and Assignment ¶

When programming, it is useful to be able to store information in variables. A variable is a string of characters and numbers associated with a piece of information. The assignment operator , denoted by the “=” symbol, is the operator that is used to assign values to variables in Python. The line x=1 takes the known value, 1, and assigns that value to the variable with name “x”. After executing this line, this number will be stored into this variable. Until the value is changed or the variable deleted, the character x behaves like the value 1.

TRY IT! Assign the value 2 to the variable y. Multiply y by 3 to show that it behaves like the value 2.

A variable is more like a container to store the data in the computer’s memory, the name of the variable tells the computer where to find this value in the memory. For now, it is sufficient to know that the notebook has its own memory space to store all the variables in the notebook. As a result of the previous example, you will see the variable “x” and “y” in the memory. You can view a list of all the variables in the notebook using the magic command %whos .

TRY IT! List all the variables in this notebook

Note that the equal sign in programming is not the same as a truth statement in mathematics. In math, the statement x = 2 declares the universal truth within the given framework, x is 2 . In programming, the statement x=2 means a known value is being associated with a variable name, store 2 in x. Although it is perfectly valid to say 1 = x in mathematics, assignments in Python always go left : meaning the value to the right of the equal sign is assigned to the variable on the left of the equal sign. Therefore, 1=x will generate an error in Python. The assignment operator is always last in the order of operations relative to mathematical, logical, and comparison operators.

TRY IT! The mathematical statement x=x+1 has no solution for any value of x . In programming, if we initialize the value of x to be 1, then the statement makes perfect sense. It means, “Add x and 1, which is 2, then assign that value to the variable x”. Note that this operation overwrites the previous value stored in x .

There are some restrictions on the names variables can take. Variables can only contain alphanumeric characters (letters and numbers) as well as underscores. However, the first character of a variable name must be a letter or underscores. Spaces within a variable name are not permitted, and the variable names are case-sensitive (e.g., x and X will be considered different variables).

TIP! Unlike in pure mathematics, variables in programming almost always represent something tangible. It may be the distance between two points in space or the number of rabbits in a population. Therefore, as your code becomes increasingly complicated, it is very important that your variables carry a name that can easily be associated with what they represent. For example, the distance between two points in space is better represented by the variable dist than x , and the number of rabbits in a population is better represented by nRabbits than y .

Note that when a variable is assigned, it has no memory of how it was assigned. That is, if the value of a variable, y , is constructed from other variables, like x , reassigning the value of x will not change the value of y .

EXAMPLE: What value will y have after the following lines of code are executed?

WARNING! You can overwrite variables or functions that have been stored in Python. For example, the command help = 2 will store the value 2 in the variable with name help . After this assignment help will behave like the value 2 instead of the function help . Therefore, you should always be careful not to give your variables the same name as built-in functions or values.

TIP! Now that you know how to assign variables, it is important that you learn to never leave unassigned commands. An unassigned command is an operation that has a result, but that result is not assigned to a variable. For example, you should never use 2+2 . You should instead assign it to some variable x=2+2 . This allows you to “hold on” to the results of previous commands and will make your interaction with Python must less confusing.

You can clear a variable from the notebook using the del function. Typing del x will clear the variable x from the workspace. If you want to remove all the variables in the notebook, you can use the magic command %reset .

In mathematics, variables are usually associated with unknown numbers; in programming, variables are associated with a value of a certain type. There are many data types that can be assigned to variables. A data type is a classification of the type of information that is being stored in a variable. The basic data types that you will utilize throughout this book are boolean, int, float, string, list, tuple, dictionary, set. A formal description of these data types is given in the following sections.

Home » Python Basics » Python Default Parameters

Python Default Parameters

Summary : in this tutorial, you’ll learn about the Python default parameters to simplify function calls.

Introduction to Python default parameters

When you define a function , you can specify a default value for each parameter.

To specify default values for parameters, you use the following syntax:

In this syntax, you specify default values ( value2 , value3 , …) for each parameter using the assignment operator ( =) .

When you call a function and pass an argument to the parameter that has a default value, the function will use that argument instead of the default value.

However, if you don’t pass the argument, the function will use the default value.

To use default parameters, you need to place parameters with the default values after other parameters. Otherwise, you’ll get a syntax error.

For example, you cannot do something like this:

This causes a syntax error.

Python default parameters example

The following example defines the greet() function that returns a greeting message:

The greet() function has two parameters: name and message . And the message parameter has a default value of 'Hi' .

The following calls the greet() function and passes the two arguments:

Since we pass the second argument to the greet() function, the function uses the argument instead of the default value.

The following example calls the greet() function without passing the second argument:

In this case, the greet() function uses the default value of the message parameter.

Multiple default parameters

The following redefines the greet() function with the two parameters that have default values:

In this example, you can call the greet() function without passing any parameters:

Suppose that you want the greet() function to return a greeting like Hello there . You may come up with the following function call:

Unfortuntely, it returns an unexpected value:

Because when you pass the 'Hello' argument, the greet() function treats it as the first argument, not the second one.

To resolve this, you need to call the greet() function using keyword arguments like this:

• Use Python default parameters to simplify the function calls.
• Place default parameters after the non-default parameters.

• Fundamentals
• All Articles

Four ways to return a default value if None in Python

One of the most common tasks when working with variables in Python is to return a default value if a variable (or a dictionary item) is None or if it doesn’t even exist.

This quick guide explores four methods of returning a default value if a variable is None or doesn’t exist.

🎧 Debugging Jam

Calling all coders in need of a rhythm boost! Tune in to our 24/7 Lofi Coding Radio on YouTube, and let's code to the beat – subscribe for the ultimate coding groove!" Let the bug-hunting begin! 🎵💻🚀

How to return a default value if None

There are several ways to do to return a default value if a variable (or a dictionary item) is None or if it doesn’t exist:

• Standard if statement
• One-liner if/else statement
• The get() method (only dictionaries)
• The try/except statement

Let’s explore each approach with examples.

1. Standard if statement:  The simplest and most readable way of returning a default value – if a variable is None – is to use a standard if block. 

Here’s how you’d do it:

In the above example, we have a function get_name() , which is supposed to return a value to the caller. The function's returned value is stored in the name variable. If the function returns None , we set the name to User .

This way, you won't need an else block.

2. One-liner if/else statement:  The previous method could be rewritten in one line. This is probably the most Pythonic way of doing this, even though it's less intuitive than a simple if .

The above example works as it reads: set the name to 'User' if get_name() returns None . Otherwise, use get_name() return value.

3. Using or:  If you're sure the returned value is either a string or None , you can use the "value or 'default'" syntax:

This syntax returns the lefthand side value if it's  truthy . Otherwise, it'll return the value on the right.

Values that are equivalent to false (in if and while statements) in Python are:

• Any object that its __len__() method returns 0 (e.g., dictionaries, lists, tuples, empty strings, etc.)

Tip:  You can also use this technique to return a default value for empty strings.

While this works well, you should be aware the above example still returns 'User' if get_name() returns one of the above "falsy" values. However, if you know the value is either a string or None , it's an option you might want to consider.

3. The get() method (only dictionaries):  You can use the get() method of a dict object and return a default value if a specific key doesn't exist.

Let's see an example:

As you can see, if the key exists but it's None , it'll be returned. However, it might not be what you want.

To return a default value if the respective key is None , you can do so:

You can also use a try/except statement like so:

Or do it in two steps:

4. The try/except statement:  As mentioned earlier, you can use the try/except statement to return a default value if a dictionary item is None . This technique isn't limited to dictionaries, though. 

You can use them for variables too. However, you must catch the NameError exception this time.

The above snippet might seem redundant for many use cases. However, since Python doesn't have a function like isset() in PHP, this is how you can make it up.

Alright, I think it does it! I hope you found this quick guide helpful.

Thanks for reading!

Reza Lavarian Hey 👋 I'm a software engineer, an author, and an open-source contributor. I enjoy helping people (including myself) decode the complex side of technology. I share my findings on Twitter: @rezalavarian

❤️ You might be also interested in:

• [Solved] SyntaxError: cannot assign to expression here in Python
• [Solved] SyntaxError: cannot assign to literal here in Python
• SyntaxError: cannot assign to function call here in Python (Solved)
• TypeError: ‘bool’ object is not callable in Python (Fixed)
• TypeError: ‘dict’ object is not callable in Python (Fixed)

Never miss a guide like this!

Disclaimer: This post may contain affiliate links . I might receive a commission if a purchase is made. However, it doesn’t change the cost you’ll pay.

• Privacy Policy

software development and tech.

Python Default Arguments: A Complete Guide (with Examples)

In almost every Python program, you are dealing with functions that take input, perform an action, and spit out an output. More often than not, it can be useful to include a default argument value in a function. If an input argument isn’t provided, the default value is used instead. And if the input value is provided, that’s going to be used in the function.

You can add default function parameters in Python by giving a default value for a parameter in the function definition using the assignment operator ( = ).

For example:

Now the default value for the name is “ friend “.

If you call this function without a parameter:

You get the default greeting:

But if you call it with a name argument:

You get a personalized greeting using the name:

This is a complete guide to default values in Python .

You will learn what is a default argument and how to specify multiple default arguments in a function. Besides, you learn that you can use both regular arguments and default arguments in the same function.

Multiple Default Parameters in Python

You can implement Python functions with multiple default parameters. This works similarly to how you can have functions with a number of regular parameters:

• Specify the parameter name and assign it a default value.
• Then add a comma and specify the next parameter.

For instance, let’s create a function that asks for first name and last name. If these are not given, the default values are used instead:

Here are some example calls for this function:

Next, let’s take a look at how to add both default and regular parameters into a function call.

Mix Up Default Parameters and Regular Parameters

You can define a function with both default parameters and regular parameters in Python. When you call a function like this, the Python interpreter determines which variable is which based on whether it has the argument label or not.

Last but not least, let’s take a look at how default parameters are denoted in Python documentation.

Default Parameters in Python Documentation

If you read the Python documentation , you sometimes see functions that have default parameters in the function syntax.

For example, let’s take a look at the enumerate function documentation:

In this function, there is start=0 in the arguments.

This means that the enumerate function has a default argument start that is 0 by default. In other words, you can call the enumerate() function by specifying:

• iterable parameter only.
• start parameter to be something else than 0.

Today you learned about Python function default parameters.

You can provide default values for function parameters in Python. This can simplify your function calls and code.

Here is an example of a function with a default parameter value:

When you call this function without a parameter, it defaults to saying “Hello, friend” . When you call it with a name argument, it greets the person with that name.

Thanks for reading. I hope you enjoy it. Happy coding!

Further Reading

• 50 Python Interview Questions with Answers
• 50+ Buzzwords of Web Development

How to Return a default value if None in Python

Last updated: Apr 8, 2024 Reading time · 4 min

# Table of Contents

• Return a default value if None in Python
• Using None as a default argument in Python

# Return a default value if None in Python

Use a conditional expression to return a default value if None in Python.

The conditional expression will return the default value if the variable stores None , otherwise the variable is returned.

Conditional expressions are very similar to an if/else statement.

In the examples, we check if the variable stores None , and if it does, we return the string default value , otherwise, the variable is returned.

Alternatively, you can switch the order of conditions.

The code sample first checks if the variable is not None , in which case it returns it.

Otherwise, a default value is returned.

# Return a default value if None using the boolean OR operator

An alternative approach is to use the boolean OR operator.

The expression x or y returns the value to the left if it's truthy, otherwise, the value to the right is returned.

However, this approach does not explicitly check for None .

All values that are not truthy are considered falsy. The falsy values in Python are:

• constants defined to be falsy: None and False .
• 0 (zero) of any numeric type
• empty sequences and collections: "" (empty string), () (empty tuple), [] (empty list), {} (empty dictionary), set() (empty set), range(0) (empty range).

So if the value to the left is any of the aforementioned falsy values, the value to the right is returned.

This might or might not suit your use case.

If you only want to check for None , use the conditional expression from the first code snippet.

# Using None as a default argument in Python

None is often used as a default argument value in Python because it allows us to call the function without providing a value for an argument that isn't required on each function invocation.

None is especially useful for list and dict arguments.

We declared a function with 2 default parameters set to None .

Default parameter values have the form parameter = expression .

When we declare a function with one or more default parameter values, the corresponding arguments can be omitted when the function is invoked.

A None value is often used for default parameters that are not essential to the function.

None is used when the function can still run even if a value for the parameter wasn't provided.

# Use None as default arguments, not Objects

Here is an example of how using an empty dictionary as a default value for a parameter can cause issues and how we can fix it with a None value.

The get_address function has a parameter with a default value of an empty dictionary.

We called the function 2 times and stored the results in variables.

Notice that we only set the country key on one of the dictionaries but both of them got updated.

They are not evaluated each time the function is called.

When a non-primitive default parameter value, such as a dictionary or a list is mutated, it is mutated for all function calls.

To resolve the issue, set the default parameter value to None and conditionally update it in the body of the function.

The body of the function is run every time it is invoked, so the issue is resolved.

I've also written an article on how to return multiple values and only use one .

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• Why does list.reverse() return None in Python
• Purpose of 'return self' from a class method in Python
• Why does my function print None in Python [Solved]
• How to check if a variable is a Function in Python

Borislav Hadzhiev

Web Developer

Copyright © 2024 Borislav Hadzhiev

Default arguments in Python

Table of Contents

Python will enable the Python arguments to have the default values . Whereas, if the function is defined without an argument. Then the argument will have a default value. Read this article to learn more about Default arguments in Python .

What is a default value?

Python has several ways of showing syntax and the default value for function arguments. The default value will represent the function argument that has the value.

However, if no argument value can be passed during the function call. Then the default value will be provided with the help of the assignment (=) operator of the form keywordname =value

Check out the example provided below

What are the examples of Python Functions?

Example 1: calling function without the keyword arguments, example 2: calling function with keyword arguments, example 3: some invalid function calls,  default argument values in python.

In Python, when you create a function with default values, those values are set when the function is defined. However, if the default value is a list or another mutable object, it can cause unexpected behavior

Let us look into the example given below:

In conclusion, a Python function is like a mini-program within your code that performs a specific task when called. It takes input values, processes them, and can return a result. Functions are handy for organizing code, making it more readable, and allowing you to reuse the same functionality in different parts of your program.

They can have default values for some or all of their parameters, making them flexible and easy to use. Understanding how to define and call functions is a fundamental skill in Python programming that helps make your code efficient and modular.

Default arguments in Python- FAQs

Q1. what are the default arguments in python.

Ans. Default arguments are the values that are given while defining functions.

Q2. What is the default input in Python?

Ans. The input will return the string.

Q3. What are the 4 types of arguments in Python?

Ans. Default arguments, Keyword arguments (named arguments), Positional arguments and Arbitrary arguments are the 4 types of argument in Python.

Hello, I’m Hridhya Manoj. I’m passionate about technology and its ever-evolving landscape. With a deep love for writing and a curious mind, I enjoy translating complex concepts into understandable, engaging content. Let’s explore the world of tech together

Python Nested Loops

Python Functions

Leave a Comment Cancel reply

Save my name, email, and website in this browser for the next time I comment.

Reach Out to Us for Any Query

SkillVertex is an edtech organization that aims to provide upskilling and training to students as well as working professionals by delivering a diverse range of programs in accordance with their needs and future aspirations.

© 2024 Skill Vertex

Default parameter values for functions in Python

In Python, you can set default values for parameters when defining a function. The default value will be used if you omit the argument when calling the function.

Set default parameter values for functions

Position constraints of default parameter values, notes on using lists and dictionaries as default values.

See the following article for the basics of functions in Python.

• Define and call functions in Python (def, return)

If you use parameter_name=default_value in the function definition, the default value will be used when the corresponding argument is omitted during the function call.

When defining a function, placing a default parameter before an ordinary parameter without a default value causes a SyntaxError .

If a mutable object like a list or dictionary is specified as a default value, it is created when the function is defined and reused when the function is called without the corresponding argument.

Default parameter values are evaluated from left to right when the function definition is executed. This means that the expression is evaluated once, when the function is defined, and that the same “pre-computed” value is used for each call. 8. Compound statements - Function definitions — Python 3.11.3 documentation

Consider a function that takes a list or dictionary as its default parameter value and adds elements to it. When the function is called multiple times without that argument, elements will be added to the same object repeatedly.

Example for a list:

Example for a dictionary:

You can use None as a default value for a parameter. As shown in the following example, a new object will be created each time the function is called without that argument.

• None in Python

Related Categories

Related articles.

• Binarize image with Python, NumPy, OpenCV
• List installed Python packages with pip list/freeze
• Complex numbers in Python
• NumPy: Functions ignoring NaN (np.nansum, np.nanmean, etc.)
• Count the number of 1 bits in python (int.bit_count)
• pandas: Handle strings (replace, strip, case conversion, etc.)
• pandas: Get the number of rows, columns, elements (size) of DataFrame
• *args and **kwargs in Python (Variable-length arguments)
• Keywords and reserved words in Python
• pandas: Select rows by multiple conditions
• Search for a string in Python (Check if a substring is included/Get a substring position)
• numpy.where(): Manipulate elements depending on conditions
• pandas: Data binning with cut() and qcut()
• Raw strings in Python
• Find GCD and LCM in Python (math.gcd(), lcm())

• Python Course
• Python Basics
• Interview Questions
• Python Quiz
• Popular Packages
• Python Projects
• Practice Python
• AI With Python
• Learn Python3
• Python Automation
• Python Web Dev
• DSA with Python
• Python OOPs
• Dictionaries

Different Forms of Assignment Statements in Python

We use Python assignment statements to assign objects to names. The target of an assignment statement is written on the left side of the equal sign (=), and the object on the right can be an arbitrary expression that computes an object.

There are some important properties of assignment in Python :-

• Assignment creates object references instead of copying the objects.
• Python creates a variable name the first time when they are assigned a value.
• Names must be assigned before being referenced.
• There are some operations that perform assignments implicitly.

Assignment statement forms :-

1. Basic form:

This form is the most common form.

2. Tuple assignment:

When we code a tuple on the left side of the =, Python pairs objects on the right side with targets on the left by position and assigns them from left to right. Therefore, the values of x and y are 50 and 100 respectively.

3. List assignment:

This works in the same way as the tuple assignment.

4. Sequence assignment:

In recent version of Python, tuple and list assignment have been generalized into instances of what we now call sequence assignment – any sequence of names can be assigned to any sequence of values, and Python assigns the items one at a time by position.

5. Extended Sequence unpacking:

It allows us to be more flexible in how we select portions of a sequence to assign.

Here, p is matched with the first character in the string on the right and q with the rest. The starred name (*q) is assigned a list, which collects all items in the sequence not assigned to other names.

This is especially handy for a common coding pattern such as splitting a sequence and accessing its front and rest part.

6. Multiple- target assignment:

In this form, Python assigns a reference to the same object (the object which is rightmost) to all the target on the left.

7. Augmented assignment :

The augmented assignment is a shorthand assignment that combines an expression and an assignment.

There are several other augmented assignment forms:

Please Login to comment...

Similar reads.

• Python Programs
• python-basics

Improve your Coding Skills with Practice

What kind of Experience do you want to share?

Join us and get access to thousands of tutorials and a community of expert Pythonistas.

This lesson is for members only. Join us and get access to thousands of tutorials and a community of expert Pythonistas.

Assigning Default Values

00:00 Default Values Assigned to Input Parameters. You can modify the function add_item() so that the parameter quantity has a default value.

00:35 In the function signature, you’ve added the default value 1 to the parameter quantity , but this doesn’t mean that the value of quantity will always be 1 .

00:46 If you pass an argument corresponding to quantity when you call the function, then that argument will be used as the value for the parameter. However, if you don’t pass any argument, then the default value will be used.

00:59 1 in this case. Parameters with default values can’t be followed by regular parameters. You’ll see more about the order in which you can define parameters later on in this course. The function add_item() now has one required parameter and one optional parameter.

01:18 In the code example just seen, you call add_item() twice. Your first function call has a single argument, which corresponds to the required parameter item_name . In this case, quantity defaults to 1 . Your second function call has two arguments, so the default value isn’t used in this case.

01:41 You can see the output on-screen.

01:47 You can also pass required and optional arguments into a function as keyword arguments. Keyword arguments can also be referred to as named arguments. You can now revisit the first function you defined in this course and refactor it so that it also accepts a default argument.

02:31 Now when you use show_list() , you can call it with no input arguments or pass a Boolean value as a flag argument. If you don’t pass any arguments when calling the function, then the shopping list is displayed by showing each item’s name and quantity.

02:45 The function will display the same output if you pass True as an argument when calling it. However, if you use show_list(False) , only the item names are displayed.

03:04 You should avoid using flags in cases where the value of the flag alters the function’s behavior significantly. A function should only be responsible for one thing. If you want to flag to push the function into an alternative path, you may consider writing a separate function instead.

03:22 In the next section of the course, you’ll look at common values which are used as defaults.

Become a Member to join the conversation.

Learn Python practically and Get Certified .

Popular Tutorials

Popular examples, reference materials, learn python interactively, python introduction.

• Get Started With Python
• Your First Python Program
• Python Comments

Python Fundamentals

• Python Variables and Literals
• Python Type Conversion
• Python Basic Input and Output
• Python Operators

Python Flow Control

• Python if...else Statement
• Python for Loop
• Python while Loop
• Python break and continue
• Python pass Statement

Python Data types

• Python Numbers and Mathematics
• Python List
• Python Tuple
• Python String
• Python Dictionary

Python Functions

Python Function Arguments

• Python Variable Scope
• Python Global Keyword
• Python Recursion
• Python Modules
• Python Package
• Python Main function

Python Files

• Python Directory and Files Management
• Python CSV: Read and Write CSV files
• Reading CSV files in Python
• Writing CSV files in Python
• Python Exception Handling
• Python Exceptions
• Python Custom Exceptions

Python Object & Class

• Python Objects and Classes
• Python Inheritance
• Python Multiple Inheritance
• Polymorphism in Python
• Python Operator Overloading

Python Advanced Topics

• List comprehension

Python Lambda/Anonymous Function

• Python Iterators
• Python Generators
• Python Namespace and Scope
• Python Closures
• Python Decorators
• Python @property decorator
• Python RegEx

Python Date and Time

• Python datetime
• Python strftime()
• Python strptime()
• How to get current date and time in Python?
• Python Get Current Time
• Python timestamp to datetime and vice-versa
• Python time Module
• Python sleep()

Additional Topic

• Precedence and Associativity of Operators in Python
• Python Keywords and Identifiers
• Python Asserts
• Python Json

Python *args and **kwargs

Python Tutorials

Python User-defined Functions

• Python map() Function

In computer programming, an argument is a value that is accepted by a function.

Before we learn about function arguments, make sure to know about Python Functions .

• Example 1: Python Function Arguments

In the above example, the function add_numbers() takes two parameters: a and b . Notice the line,

Here, add_numbers(2, 3) specifies that parameters a and b will get values 2 and 3 respectively.

• Function Argument with Default Values

In Python, we can provide default values to function arguments.

We use the = operator to provide default values. For example,

In the above example, notice the function definition

Here, we have provided default values 7 and 8 for parameters a and b respectively. Here's how this program works

1. add_number(2, 3)

Both values are passed during the function call. Hence, these values are used instead of the default values.

2. add_number(2)

Only one value is passed during the function call. So, according to the positional argument 2 is assigned to argument a , and the default value is used for parameter b .

3. add_number()

No value is passed during the function call. Hence, default value is used for both parameters a and b .

• Python Keyword Argument

In keyword arguments, arguments are assigned based on the name of the arguments. For example,

Here, notice the function call,

Here, we have assigned names to arguments during the function call.

Hence, first_name in the function call is assigned to first_name in the function definition. Similarly, last_name in the function call is assigned to last_name in the function definition.

In such scenarios, the position of arguments doesn't matter.

• Python Function With Arbitrary Arguments

Sometimes, we do not know in advance the number of arguments that will be passed into a function. To handle this kind of situation, we can use arbitrary arguments in Python .

Arbitrary arguments allow us to pass a varying number of values during a function call.

We use an asterisk (*) before the parameter name to denote this kind of argument. For example,

In the above example, we have created the function find_sum() that accepts arbitrary arguments. Notice the lines,

Here, we are able to call the same function with different arguments.

Note : After getting multiple values, numbers behave as an array so we are able to use the for loop to access each value.

Table of Contents

• Introduction

Write a function to return a full name with a space in between.

• For example, if the first_name is John and the last_name is Doe , the return value should be John Doe .

Video: Python Function Arguments: Positional, Keywords and Default

Sorry about that.

Related Tutorials

Python Tutorial

• Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers
• Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand
• OverflowAI GenAI features for Teams
• OverflowAPI Train & fine-tune LLMs
• Labs The future of collective knowledge sharing
• About the company Visit the blog

Collectives™ on Stack Overflow

Find centralized, trusted content and collaborate around the technologies you use most.

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

Get early access and see previews of new features.

How to set default value for variable?

Imagine I have the following code in javascript

What is the Python way of initiating a variable that may be undefined?

• The answers tell you how to have a parameter with a default value, but maybe you want this: stackoverflow.com/questions/23086383/… –  Paulo Almeida Commented Mar 30, 2016 at 23:16

3 Answers 3

In the exact scenario you present, you can use default values for arguments, as other answers show.

Generically, you can use the or keyword in Python pretty similarly to the way you use || in JavaScript; if someone passes a falsey value (such as a null string or None ) you can replace it with a default value like this:

This can be useful when your value comes from a file or user input:

Or when you want to use an empty container for a default value, which is problematic in regular Python (see this SO question ):

• It's worth mentioning, for None specifically, do string = string if string is not None else "defaultValue" . Reference: How to "test" NoneType in python? –  wjandrea Commented Jul 13, 2022 at 14:54
• I wouldn't use sequence or , cause it's too loose. For example, if I accidentally passed in the integer 0 , I'd expect a TypeError , but this'd silently use the default. This'd be better: if sequence is None or len(sequence) == 0: sequence = [] . But thinking about that, why bother swapping out empty sequences? If you're actually intending to only replace None , do that explicitly instead of using or : sequence = sequence if sequence is not None else [] . –  wjandrea Commented Jul 13, 2022 at 15:13

For a function parameter, you can use a default argument value :

You can use default values:

See https://docs.python.org/2/tutorial/controlflow.html#default-argument-values

Your Answer

Reminder: Answers generated by artificial intelligence tools are not allowed on Stack Overflow. Learn more

Sign up or log in

Post as a guest.

Required, but never shown

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy .

Not the answer you're looking for? Browse other questions tagged python undefined or ask your own question .

• Featured on Meta
• We've made changes to our Terms of Service & Privacy Policy - July 2024
• Bringing clarity to status tag usage on meta sites
• Feedback requested: How do you use tag hover descriptions for curating and do...

Hot Network Questions

• How to allow just one user to use SSH?
• Why is there a custom to say "Kiddush Levana" (Moon Blessing) on Motsaei Tisha Be'av
• How common is it for external contractors to manage internal teams, and how can we navigate this situation?
• Is my encryption format secure?
• Are "lie low" and "keep a low profile" interchangeable?
• Kyoto is a famous tourist destination/area/site/spot in Japan
• Is magnetic flux in a transformer proportional to voltage or current?
• Who is affected by Obscured areas?
• LED lights tripping the breaker when installed on the wrong direction?
• Associated with outsiders
• Easyjet denied EU261 compensation for flight cancellation during Crowdstrike: Any escalation or other recourse?
• Generating Carmichaeal numbers in polynomial time
• I need to draw as attached image
• Do temperature variations make trains on Mars impractical?
• When does bundling wire with zips become a problem?
• ~1980 UK TV: very intelligent children recruited for secret project
• How did this zucchini plant cling to the zip tie?
• What do smooth signatures give you?
• Is math a bad discipline for teaching jobs or is it just me?
• Fitting the 9th piece into the pizza box
• Font showing in Pages but not in Font book (or other apps)
• Ubuntu/Linux: Use WiFi to access a specific LPD/LPR network print server and use Ethernet to access everything else
• Just got a new job... huh?
• John 1:1, "the Word was with God, and the Word was God." Vs2, He was in the beginning with God. Does this not prove Jesus existed before Genesis 1:1?