python conditional assignment without else

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! 😊

One line if without else in Python

by Nathan Sebhastian

Posted on Feb 22, 2023

Reading time: 4 minutes

If you don’t have an else statement, then you can write a one line if statement in Python by removing the line break as follows:

There are 3 different ways you can create a one line if conditional without an else statement:

• The regular if statement in one line
• Using the ternary operator syntax
• Shorthand syntax with the and operator

This tutorial shows you examples of writing intuitive one line if statements in practice.

1. One line if statement

In the following example, the if statement prints something if x value is greater than 10 :

Now here’s how you convert the code into one line if statement:

Yup! Just remove the line break and you’re good to go.

If you have more than one line in the if body, you can use a semicolon to mark the end of the statements. See the example below:

But keep in mind that this code violates Python coding conventions by defining multiple statements in one line.

It’s also harder to read when you have complex statements inside the if body. Still, the code works well when you have simple conditionals.

2. Ternary operator syntax without else

The Python ternary operator is used to create a one line if-else statement.

It comes in handy when you need to write a short and simple if-else statement as follows:

You can read this article to learn more about how ternary operators work in Python.

You can use the ternary operator to write a one line if statement without an else as follows:

By returning None , Python will do nothing when the else statement is executed.

Although this one line if statement works, it’s not recommended when you have an assignment in your if body as follows:

Using the ternary operator, you still need to assign the original value of y in the else statement as follows:

The ternary operator doesn’t allow you to discard the else statement, so this code redundantly assigns the value of y to y in the else statement.

It’s better to use a regular if statement as follows:

Using a regular if statement has less repetition and easier to read.

3. Shorthand syntax with the and operator

The and operator can be used to shorthand an if statement because this operator executes the second operand only when the first operand returns True .

Suppose you have an if statement as follows:

You can use the and operator to rewrite the code above as follows:

The print() function above is only executed when the expression on the left side of the and operator returns True .

But this method also falls short when you need to do an assignment as it will raise an error:

If your conditional involves an assignment, then you need to use the regular if statement.

This tutorial has shown you examples of writing a one line if without else statement in Python.

In practice, writing a one line if statement is discouraged as it means you’re writing at least two statements in one line: the condition and the code to run when that condition is True .

Just because you can, doesn’t mean you should. Writing a regular if statement with line breaks and indents provides you with a clean and consistent way to define conditionals in your code.

I hope this tutorial helps. Happy coding! 👍

Take your skills to the next level ⚡️

I'm sending out an occasional email with the latest tutorials on programming, web development, and statistics. Drop your email in the box below and I'll send new stuff straight into your inbox!

Hello! This website is dedicated to help you learn tech and data science skills with its step-by-step, beginner-friendly tutorials. Learn statistics, JavaScript and other programming languages using clear examples written for people.

Learn more about this website

Connect with me on Twitter

Or LinkedIn

Type the keyword below and hit enter

Click to see all tutorials tagged with:

• Learn Python
• Python Lists
• Python Dictionaries
• Python Strings
• Python Functions
• Learn Pandas & NumPy
• Pandas Tutorials
• Numpy Tutorials
• Learn Data Visualization
• Python Seaborn
• Python Matplotlib

Inline If in Python: The Ternary Operator in Python

• September 16, 2021 December 20, 2022

In this tutorial, you’ll learn how to create inline if statements in Python. This is often known as the Python ternary operator, which allows you to execute conditional if statements in a single line, allowing statements to take up less space and often be written in my easy-to-understand syntax! Let’s take a look at what you’ll learn.

The Quick Answer: Use the Python Ternary Operator

Table of Contents

What is the Python Ternary Operator?

A ternary operator is an inline statement that evaluates a condition and returns one of two outputs. It’s an operator that’s often used in many programming languages, including Python, as well as math. The Python ternary operator has been around since Python 2.5, despite being delayed multiple times.

The syntax of the Python ternary operator is a little different than that of other languages. Let’s take a look at what it looks like:

Now let’s take a look at how you can actually write an inline if statement in Python.

How Do you Write an Inline If Statement in Python?

Before we dive into writing an inline if statement in Python, let’s take a look at how if statements actually work in Python. With an if statement you must include an if , but you can also choose to include an else statement, as well as one more of else-ifs, which in Python are written as elif .

The traditional Python if statement looks like this:

This can be a little cumbersome to write, especially if you conditions are very simple. Because of this, inline if statements in Python can be really helpful to help you write your code faster.

Let’s take a look at how we can accomplish this in Python:

This is significantly easier to write. Let’s break this down a little bit:

• We assign a value to x , which will be evaluated
• We declare a variable, y , which we assign to the value of 10, if x is True. Otherwise, we assign it a value of 20.

We can see how this is written out in a much more plain language than a for-loop that may require multiple lines, thereby wasting space.

Tip! This is quite similar to how you’d written a list comprehension. If you want to learn more about Python List Comprehensions, check out my in-depth tutorial here . If you want to learn more about Python for-loops, check out my in-depth guide here .

Now that you know how to write a basic inline if statement in Python, let’s see how you can simplify it even further by omitting the else statement.

How To Write an Inline If Statement Without an Else Statement

Now that you know how to write an inline if statement in Python with an else clause, let’s take a look at how we can do this in Python.

Before we do this, let’s see how we can do this with a traditional if statement in Python

You can see that this still requires you to write two lines. But we know better – we can easily cut this down to a single line. Let’s get started!

We can see here that really what this accomplishes is remove the line break between the if line and the code it executes.

Now let’s take a look at how we can even include an elif clause in our inline if statements in Python!

Check out some other Python tutorials on datagy.io, including our complete guide to styling Pandas and our comprehensive overview of Pivot Tables in Pandas !

How to Write an Inline If Statement With an Elif Statement

Including an else-if, or elif , in your Python inline if statement is a little less intuitive. But it’s definitely doable! So let’s get started. Let’s imagine we want to write this if-statement:

Let’s see how we can easily turn this into an inline if statement in Python:

This is a bit different than what we’ve seen so far, so let’s break it down a bit:

• First, we evaluate is x == 1. If that’s true, the conditions end and y = 10.
• Otherwise, we create another condition in brackets
• First we check if x == 20, and if that’s true, then y = 20. Note that we did not repeated y= here.
• Finally, if neither of the other decisions are true, we assign 30 to y

This is definitely a bit more complex to read, so you may be better off creating a traditional if statement.

In this post, you learned how to create inline if statement in Python! You learned about the Python ternary operator and how it works. You also learned how to create inline if statements with else statements, without else statements, as well as with else if statements.

To learn more about Python ternary operators, check out the official documentation here .

Nik Piepenbreier

Nik is the author of datagy.io and has over a decade of experience working with data analytics, data science, and Python. He specializes in teaching developers how to use Python for data science using hands-on tutorials. View Author posts

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

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

Python One Line Conditional Assignment

Problem : How to perform one-line if conditional assignments in Python?

Example : Say, you start with the following code.

You want to set the value of x to 42 if boo is True , and do nothing otherwise.

Let’s dive into the different ways to accomplish this in Python. We start with an overview:

Exercise : Run the code. Are all outputs the same?

Next, you’ll dive into each of those methods and boost your one-liner superpower !

Method 1: Ternary Operator

The most basic ternary operator x if c else y returns expression x if the Boolean expression c evaluates to True . Otherwise, if the expression c evaluates to False , the ternary operator returns the alternative expression y .

Let’s go back to our example problem! You want to set the value of x to 42 if boo is True , and do nothing otherwise. Here’s how to do this in a single line:

While using the ternary operator works, you may wonder whether it’s possible to avoid the ...else x part for clarity of the code? In the next method, you’ll learn how!

If you need to improve your understanding of the ternary operator, watch the following video:

You can also read the related article:

• Python One Line Ternary

Method 2: Single-Line If Statement

Like in the previous method, you want to set the value of x to 42 if boo is True , and do nothing otherwise. But you don’t want to have a redundant else branch. How to do this in Python?

The solution to skip the else part of the ternary operator is surprisingly simple— use a standard if statement without else branch and write it into a single line of code :

To learn more about what you can pack into a single line, watch my tutorial video “If-Then-Else in One Line Python” :

Method 3: Ternary Tuple Syntax Hack

A shorthand form of the ternary operator is the following tuple syntax .

Syntax : You can use the tuple syntax (x, y)[c] consisting of a tuple (x, y) and a condition c enclosed in a square bracket. Here’s a more intuitive way to represent this tuple syntax.

In fact, the order of the <OnFalse> and <OnTrue> operands is just flipped when compared to the basic ternary operator. First, you have the branch that’s returned if the condition does NOT hold. Second, you run the branch that’s returned if the condition holds.

Clever! The condition boo holds so the return value passed into the x variable is the <OnTrue> branch 42 .

Don’t worry if this confuses you—you’re not alone. You can clarify the tuple syntax once and for all by studying my detailed blog article.

Related Article : Python Ternary — Tuple Syntax Hack

Python One-Liners Book: Master the Single Line First!

Python programmers will improve their computer science skills with these useful one-liners.

Python One-Liners will teach you how to read and write “one-liners”: concise statements of useful functionality packed into a single line of code. You’ll learn how to systematically unpack and understand any line of Python code, and write eloquent, powerfully compressed Python like an expert.

The book’s five chapters cover (1) tips and tricks, (2) regular expressions, (3) machine learning, (4) core data science topics, and (5) useful algorithms.

Detailed explanations of one-liners introduce key computer science concepts and boost your coding and analytical skills . You’ll learn about advanced Python features such as list comprehension , slicing , lambda functions , regular expressions , map and reduce functions, and slice assignments .

You’ll also learn how to:

• Leverage data structures to solve real-world problems , like using Boolean indexing to find cities with above-average pollution
• Use NumPy basics such as array , shape , axis , type , broadcasting , advanced indexing , slicing , sorting , searching , aggregating , and statistics
• Calculate basic statistics of multidimensional data arrays and the K-Means algorithms for unsupervised learning
• Create more advanced regular expressions using grouping and named groups , negative lookaheads , escaped characters , whitespaces, character sets (and negative characters sets ), and greedy/nongreedy operators
• Understand a wide range of computer science topics , including anagrams , palindromes , supersets , permutations , factorials , prime numbers , Fibonacci numbers, obfuscation , searching , and algorithmic sorting

By the end of the book, you’ll know how to write Python at its most refined , and create concise, beautiful pieces of “Python art” in merely a single line.

Get your Python One-Liners on Amazon!!

Conditional expression (ternary operator) in Python

Python has a conditional expression (sometimes called a "ternary operator"). You can write operations like if statements in one line with conditional expressions.

• 6. Expressions - Conditional expressions — Python 3.11.3 documentation

Basics of the conditional expression (ternary operator)

If ... elif ... else ... by conditional expressions, list comprehensions and conditional expressions, lambda expressions and conditional expressions.

See the following article for if statements in Python.

• Python if statements (if, elif, else)

In Python, the conditional expression is written as follows.

The condition is evaluated first. If condition is True , X is evaluated and its value is returned, and if condition is False , Y is evaluated and its value is returned.

If you want to switch the value based on a condition, simply use the desired values in the conditional expression.

If you want to switch between operations based on a condition, simply describe each corresponding expression in the conditional expression.

An expression that does not return a value (i.e., an expression that returns None ) is also acceptable in a conditional expression. Depending on the condition, either expression will be evaluated and executed.

The above example is equivalent to the following code written with an if statement.

You can also combine multiple conditions using logical operators such as and or or .

• Boolean operators in Python (and, or, not)

By combining conditional expressions, you can write an operation like if ... elif ... else ... in one line.

However, it is difficult to understand, so it may be better not to use it often.

The following two interpretations are possible, but the expression is processed as the first one.

In the sample code below, which includes three expressions, the first expression is interpreted like the second, rather than the third:

By using conditional expressions in list comprehensions, you can apply operations to the elements of the list based on the condition.

See the following article for details on list comprehensions.

• List comprehensions in Python

Conditional expressions are also useful when you want to apply an operation similar to an if statement within lambda expressions.

In the example above, the lambda expression is assigned to a variable for convenience, but this is not recommended by PEP8.

Refer to the following article for more details on lambda expressions.

• Lambda expressions in Python

Related Categories

Related articles.

• Shallow and deep copy in Python: copy(), deepcopy()
• Composite two images according to a mask image with Python, Pillow
• OpenCV, NumPy: Rotate and flip image
• pandas: Check if DataFrame/Series is empty
• Check pandas version: pd.show_versions
• Python if statement (if, elif, else)
• pandas: Find the quantile with quantile()
• Handle date and time with the datetime module in Python
• Get image size (width, height) with Python, OpenCV, Pillow (PIL)
• Convert between Unix time (Epoch time) and datetime in Python
• Convert BGR and RGB with Python, OpenCV (cvtColor)
• Matrix operations with NumPy in Python
• pandas: Replace values in DataFrame and Series with replace()
• Uppercase and lowercase strings in Python (conversion and checking)
• Calculate mean, median, mode, variance, standard deviation in Python

• 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 Ways of Using Inline if in Python

Python offers a concise and expressive way to handle conditional logic in your code by using inline if. Whether you need an essential conditional expression or want to nest multiple conditions, inline can make your code more readable and maintainable. Among these tools is the inline if statement, an invaluable asset for crafting short, yet intuitive, conditional assignments. Also known as the ternary operator or conditional expression, the inline if allows for swift evaluations and assignments based on conditions

Table of Content

Different ways of using inline if in python, basic inline if without else, basic inline using if -else, using inline if with nested, using inline if in list comprehensions, using inline if with function calls, advantages and disadvantages of using inline if.

In this example, we are comparing and finding the minimum number by using the ternary operator .

In this example, if x is even, the variable message will be assigned the string “Even,” and if x is odd, it will be assigned the string “Odd.”

In this example, we use nested inline if statements to determine the relationship between the values of x and y.

In this example, we use inline if within a list comprehension to include only even numbers in the list of squares.

In this example, the operation variable is assigned the square function if n is even and the cube function if n is odd. The appropriate function is then called to calculate the result.

• Conciseness: Inline if statements make your code shorter and more readable by reducing the need for multiple lines of code for simple conditionals.
• Clarity: They can improve code clarity when used appropriately, especially in situations where the condition and expressions are short and straightforward.
• Readability: Inline if can make your code more readable by keeping the conditional logic close to where it’s used.

Disadvantages

• Limited Complexity: They are not suitable for complex conditions or multiple statements within the condition or expressions, which can reduce code readability.
• Overuse: Overusing inline if can make your code less readable, as complex expressions can become hard to understand in a single line.
• Debugging: Debugging can be more challenging when using inline if, as you can’t set breakpoints within the conditional expression.

Similar Reads

• Geeks Premier League
• Geeks Premier League 2023

Please Login to comment...

Improve your coding skills with practice.

What kind of Experience do you want to share?