Python Keywords

Python Keywords

Keywords in Python play an important role in shaping Python's syntax and functionalities. These Python-reserved words have specific meanings. We cannot use them as identifiers or variable names. For example, we cannot define any variable as: def = 5 because def is a reserved keyword in Python.

The keywords in Python are reserved words that hold a predefined meaning in the Python language. These words are useless for any other purpose, hence it ensures an unambiguous interpretation by the Python interpreter.

Keywords in Python cover a variety of functionalities, ranging from defining control structures like if, else, and while, to managing functions with the usage of def and handling exceptions with try and except blocks. Each keyword in Python plays an important role in creating the logic and behavior of the Python scripts (or codes).

One of the most important features of Python is its easy readability, and keywords play a crucial role in gaining this feature. The keywords in Python provide a common language for developers to communicate with the interpreter and fellow programmers. For example, whenever we encounter keywords like for or in in our code, we instantly know that we are dealing with loops encouraging a shared understanding within the Python community.

Not only this but Python's extensibility is noticeable in its ability to evolve and introduce new keywords with the introduction of each version. As developers accept these additions, the Python language adapts and expands its capabilities and ensures it remains useful and updated.

Some of the most commonly used Keywords in Python are:

• if, else, elif: The if, else, and elif keywords allow us to create conditional statements. For example, if we want to develop a weather app that displays different messages based on the current temperature. So, we can use these keywords to deal with such situations. Let's see a code for the same scenario.
  • Example:

• for and while: These keywords in Python are related to iteration. Iteration is a common programming language concept, and in Python language, we use the for and while keywords to achieve iteration. Let us think of a situation where we need to process a list of items or repeat a task until a certain condition is met. These keywords provide the capability for creating loops, making the code concise and efficient.
  • Example:

• def and return: Functions are the building blocks of any programming language. We use Python's def and return keywords to create a functional block and to return something from a function. For example, if we are developing a financial application, we can use these keywords to define a function that calculates the compound interest based on user inputs. We can then use the return keyword to return the calculated compound interest.
  • Example:

• class and self: With the self keyword, we can refer to the instances of a class within its methods. For example, we can think of a situation where we have to design a game. The class keyword can be used to create player objects, and the self keyword can help to manage the attributes and behaviours of the player.
  • Example:

List of Python Keywords

Let us look at the list of various keywords in Python.

• False: It is the boolean value that represents false. It is often used in conditional statements and expressions to control the flow of a Python program. For example, in an if statement, the indented block of code (next block of code) is executed only if the provided if the condition evaluates to True. The False keyword, on the other hand, helps in creating more readable and expressive code by explicitly stating a condition's negation.
• None: The None keyword shows that a value is not present or a null value is present there. It is a single object used to show that a variable or expression has no specific data assigned to it. When a function does not explicitly return any value, it implicitly returns a None value. Python developers often use the None keyword to initialize the variables before assigning them a value or to indicate the absence of a valid result. Not only this but the None keyword is commonly used in conditional statements to check if a variable has been set or if a function has produced a valid output or not.
• True: The True keyword is a Boolean value that represents the truth or validity of a statement. It is one of the two built-in Boolean values among False and True. True is often used in conditional statements and logical operations to indicate that a given expression or condition is valid. The True keyword is fundamental for controlling the flow of a program. It helps to make decisions based on logical conditions in Python code.
• and: The and keyword in Python is a logical operator and it is used for combining multiple conditions in any boolean expression. It returns True only if both the conditions on its left and right sides are True; otherwise, it evaluates to False. For example, in the expression x > 5 and y < 10, the overall result is True only if both x is greater than 5 and y is less than 10. The and keyword is used for building compound conditions in control flow statements like if statements and while loops. It also enables the developers to create more complex decision-making structures in their code.
• as: The as keyword is used for creating alias names during the import statements. It allows us to rename a module or an entity within a module. It provides a more concise name to use in the code. For example, import math as m lets us refer to the math module as m in our code. Similarly, when we are handling exceptions in Python, the except Exception as e allows us to reference the caught exception as e. The as keyword enhances code readability and can help us avoid naming conflicts in larger projects.
• assert: The assert keyword is used for debugging and testing our Python code. It allows us to check if a given condition is True, and if it is not True, it raises an AssertionError exception. This halts the program's execution. It is commonly used to validate assumptions about the state of the code during the development phase. When the condition is False, the assert statement provides a clear indication that the behaviour is unaccepted. It aids in identifying and fixing issues in the code. It is crucial to note that using the assert in production code is not recommended, as it can be disabled globally, impacting program behaviour.
• break: The break keyword in Python is used within loops (such as the for loop or while loop) to exit the loop's execution when a specified condition is met. When the break keyword is encountered, the Python code immediately terminates the loop, and the control is then transferred to the statement present after the loop. Hence, the break keyword allows efficient program flow control. It comes in handy especially when a certain condition is required to exit early from a loop structure. The break statement is particularly useful to improve code readability and to avoid unnecessary iterations when the desired condition is already satisfied.
• class: The class keyword is used to define a blueprint for creating objects. We can also create a class having shared attributes and behaviours. Class helps to encapsulate the data and functions into a single unit, and hence promotes code organization and reusability. Objects created using a class are instances that inherit its properties. Classes also help us with various object-oriented programming (OOP) principles such as encapsulation, inheritance, and polymorphism. With the help of classes, developers can model real-world entities, structure code logically, and facilitate modular design.
• continue: The continue keyword in Python is used within loops (such as the for loop or while loop) to skip the rest of the code inside the loop for the current iteration and move to the next iteration. When the continue statement is encountered, the program goes to the next iteration without even executing the remaining code present below in the loop. The continue keyword allows skipping specific iterations based on a certain condition. It enables more controlled flow within loops.
• def: The def keyword is used to define a function within Python programming. Functions are blocks of reusable code that perform a specific task written inside the code block. When we use the def keyword followed by a function name and parameters, we are creating a function definition. The indented block of code below the def statement specifies the actions that the function will execute when this function is called later in the code.
• del: The del keyword is used to delete objects, variables, or elements present in the memory block. When the del keyword is applied to a variable, it removes the reference to the object. It allows memory to be reclaimed by the garbage collector hence faster and efficient code execution is guaranteed. It can also be used to delete items from lists or elements from dictionaries. For example, del my_list[2] will remove the element at index 2 from the list. Please note that we should be cautious when using del as it permanently removes the specified value out of the memory. Now, if we are attempting to use the deleted variable or element after it has been deleted then it will result in an error.
• if: The if keyword is a conditional statement used to execute a block of code only if a specified condition is true. It enables us to create the decision-making structures in our Python programs.
• elif: elif is a concatenation of else if. It is a keyword used in conditional statements (if-else statements) to specify multiple conditions within the Python code. When the initial if statement evaluates to false, the program moves to the elif block, where a new condition is checked and this goes on until else is met. For example, if the elif condition is true, the corresponding block of code is executed. If not, the program can proceed to additional elif blocks or an optional else block. The elif condition allows the implementation of a series of conditions, which enables developers to write more complex decision-making structures in Python codes or scripts.
• else: The else keyword is used with the above discussed conditional statements, such as if, elif, or while. When the condition specified in the given if statement is false, the code block under the else block is executed. The else keyword provides an alternative set of instructions to be carried out when the initial condition is not correct. The else block enhances the flexibility of control flow in Python code thus allowing various paths of execution based on the evaluation of the conditions. It is particularly useful for handling situations where the primary condition is not satisfied thus offering a fallback or default behavior in the code.
• except: The except keyword is used in exception handling to catch and handle various types of errors or exceptions that may occur during the execution of a program. It is part of the try-except block structure, where code within the try block is attempted, and if an exception occurs, the following except block is executed. This helps us to prevent programs from crashing and it allows us to handle the errors without breaking the flow of the code. Multiple except blocks can be used to handle different types of exceptions, ensuring an optimized and correct response to various error scenarios.
• finally: The finally keyword is used with the try and except block to define a set of statements that will be executed even if an exception is raised or not. The finally block ensures that clean code or finalized code is executed, making it useful for tasks like closing files or releasing resources. Whether an exception occurs or not, the finally block is guaranteed to run, providing a mechanism for handling cleanup operations. This keyword enhances code robustness by ensuring that essential cleanup tasks are performed, even in the presence of exceptions.
• for: The for keyword is used to iterate over a sequence of data (such as a list, tuple, dictionary, or string) or various other iterable objects. It simplifies the process of traversing elements in a collection without explicitly managing loop variables. The for loop executes a block of code for each item in the iterable. It assigns the current item to a variable in each iteration and then the following code is executed if the condition provided in the for block evaluates true. This concise and readable syntax enhances code efficiency, making it a fundamental use for repetitive tasks. The for loop in Python provides more readability and support and it emphasizes simplicity and elegance in Python programming.
• from: The from keyword is used in import statements to import specific attributes or submodules from a module rather than importing the entire module. It allows us to streamline our code by bringing in only what we need. It enhances the code clarity and also helps to namespace conflicts. For example, from module import function imports only the specified function from the module. In this way, we can target the import and this approach simplifies code maintenance and promotes a cleaner, more modular code structure.
• global: The global keyword is often used to indicate that a variable declared within a function should be treated as a global variable, rather than a local variable. When a variable is declared as global inside a function, it allows the function to modify the value of the global variable directly, instead of creating a new local variable with the same name. This is particularly useful when we want to alter the value of a variable defined outside the current function scope. The use of global helps in maintaining a single, shared instance of the variable across different scopes in the program. For example, it can be quite useful to make a global counter of a specific work.
• import: The import keyword is used to include external modules or libraries into a program and it enables the use of functions, classes, and variables defined in those imported modules. It allows us to use the existing code and avoid redundancy. For example, import math imports or brings in the math module and allows access to mathematical functions like sqrt and sin. Additionally, we can also import the custom modules or packages by using import module_name or from module_name import specific_function. The import statement enhances code modularity and code reusability by allowing us to integrate the external code components.
• in: The in keyword is used to check whether a specific element is present in a sequence or not. For example, if a specific element is present in a list tuple or string. It returns a Boolean value, True if the element is found, and False otherwise. For example, x in my_list will evaluate to True if the variable x is an element in the list my_list. This small but useful keyword simplifies the process of searching for items within any sequence data structure. It enhances the code readability and efficiency.
• is: The 'is' keyword is used to validate object identification by determining whether two variables correspond to the same object in memory rather than having identical values. If both variables link to the same object, it returns True; otherwise, it returns False. Unlike the == operator, which tests for value equality, the 'is' operator looks for identical objects. It is frequently used with immutable types like numbers and strings, but when used with mutable objects, unexpected behaviour may occur owing to shared references.
• lambda: The term 'lambda' is used to define anonymous functions, often known as lambda functions. The syntax 'lambda arguments: expression' is used to declare these functions without a name. Lambda functions are often used for short, simple operations and are commonly employed in functional programming constructs like map, filter, and reduce. They give an efficient approach to defining short functions in line without the requirement for a complete function specification. They are, however, restricted to a single expression and are typically used in cases when a full function description is unneeded or onerous.
• nonlocal: The 'nonlocal' keyword is used within nested functions to signal that a variable should be handled as a non-local variable, bridging the gap between local and global scopes. It enables the change of a variable in an outside (but non-global) scope while avoiding the creation of a new local variable with the same name. This is very handy when working with closures, when one function is written inside another, and you wish to change a variable from the outer function within the inner function. The nonlocal keyword aids in maintaining a relationship between the variable's inner and outside scopes.
• not: The logical operator 'not' in Python is used to negate the truth value of a statement. It returns 'True' if the provided phrase is False, and False otherwise. not x, for example, evaluates to True if x is False and to False if x is True. It is a key component of boolean logic, allowing programmers to build conditional statements and regulate flow based on the logical state of variables. This operator is required in Python programming for expressing negation and developing complicated decision-making structures.
• or: In Python, the or keyword is a logical operator that is used for Boolean expressions. It returns True if at least one of the operands is True; otherwise, it returns False. It is often employed to combine the multiple conditions in an if statement, where the block of code executes if any of the conditions are true. For example, if x > 0 or y > 0: will evaluate True if either x or y (or both) are greater than zero. The or operator provides a flexible way to create compound conditions and enhance the control flow of Python programs.
• pass: The pass keyword is a null operation or a no-op statement. It serves as the placeholder where syntactically some code is required but no action is required. It is often used in situations where the program structure is being developed and the actual implementation of a particular block of code is deferred. The pass statement does nothing and allows the program to pass over that section without raising any errors. It is particularly useful in creating minimal code structures, such as empty functions or classes, to be filled in later.
• raise: The raise keyword is used to explicitly raise an exception, causing a program's usual flow to be disrupted. When an error occurs, the programmer can use raise to produce and issue a custom exception or utilize a preset one. It is composed of the keyword raise followed by the exception type or an instance of an exception class. This aids in dealing with unforeseen events and gives you more control over mistake management. The use of 'raise' is critical for developing robust and fault-tolerant programming, since it allows developers to communicate and resolve unusual conditions during program execution.
• return: The return keyword in Python is used to exit from a function and then return some value to the function or statement that called it. When a function finds the return statement, the execution ends immediately and the execution is sent to the specified value (back to the code that called the function). The return keyword allows functions to produce results that can be used in other parts of the code. If a return statement is not present or it does not return a value, the function returns None by default. The return keyword is important for creating modular and reusable code. It enables us to transfer data from functions to the rest of the program.
• try: The try keyword is one of the most useful keywords in Python programming that is used for exception handling. It allows us to write code that might raise an exception within a try block, and we can then define how to handle those exceptions (if arise) in the corresponding except blocks. If an exception occurs in the try block, the control is transferred to the appropriate except block defined by the programmer. This mechanism helps us to prevent programs from crashing and allows us to handle errors and exceptions gracefully. Additionally, the try block can also be followed by a finally block to specify the code that should be executed regardless of whether an exception occurred or not, providing a way to clean up the allocated resources.
• while: The while keyword is used to create a while loop in Python programming. A while loop repeatedly executes a block of code as long as the specified condition is true. The while loop provides a way to create dynamic and repetitive processes. It allows us to iterate until the provided certain condition is no longer correct. We should be careful while defining the while loop to ensure that the condition eventually becomes false to avoid infinite loops.
• with: The with keyword in Python is used for context management. It simplifies resource management like file handling and other such tasks. It ensures proper initialization and cleanup by defining a block of code within the context manager. The context manager has methods like the __enter__ method which is invoked at the beginning and the __exit__method which is called at the end (even if an exception occurs). For example, when we use with open('file.txt', 'r') as file:, it ensures that the file is properly opened and closed. It enhances code readability and avoids common dangers related to resource management. Thus, the with keyword helps us to make a convenient and reliable mechanism in Python for working with various external files and resources.
• yield: The yield keyword in Python programming is used in a function to create generators. When the yield function is called, an iterator is returned but it does not execute the entire function immediately. Instead of this, it yields one value at a time during each iteration hence it allows the function to be paused and resumed. This is particularly useful for handling large datasets or for performing lazy evaluation, as it conserves memory and improves overall performance. The generator function retains its state between the function calls and it enables an efficient processing of large datasets without even loading the data entirely into memory.

How to Identify Python Keywords?

Keywords in Python are case-sensitive and we cannot use them as identifiers. To identify the keywords in Python, we can always refer to the official Python documentation or we can also use a built-in keyword module named keyword. The keyword module provides us with a lot of functions. Now, to get the list of keywords in Python, we can use the kwlist. Let's see the code for it.

This simple Python script imports the keyword module and it utilizes the kwlist attribute of the module to fetch the complete list of Python keywords. The function then prints each of the keywords using the for loop. It can always be used as a quick reference for developers.

Explanation:

• import keyword: This statement imports the keyword module, and grants access to keyword-related functions and attributes.
• keyword.kwlist: Provides us with a list containing all the Python keywords.
• identify_keywords(): A user-defined function that prints each keyword from the kwlist attribute.

By using the above code snippet, we can effortlessly identify the Python keywords. Whether you're a beginner or an experienced coder, this approach ensures a quick and reliable way to stay informed about the reserved words in Python. Using this approach, you do not need to remember the entire list.

Python Keywords and Their Usage

Let us now look at the various keywords in Python and their use cases.

and, or, not:

They are the logical operators that help us to combine and manipulate conditions in Python programming. These logical operators help us to achieve decision-making in our code.

Example:

Output:

if, elif, else

These keywords are used with conditional statements in Python programming. These keywords determine the flow of execution based on the specified conditions.

Example:

Output:

while, for:

Looping is one of the most important concepts of any programming language. The while and for keywords control the repetitive execution of code and allow efficient iteration.

Example:

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in:

The in is an important keyword that deals with membership. It checks if a value exists within a sequence or not. It simplifies the process of searching through lists, strings, or any other iterable objects.

Example:

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is:

The it keyword is used for identity testing. It checks if two variables reference the same object in memory or not. It ensures that the comparison is precise or not.

Example:

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global, nonlocal:

When dealing with a variable scope, the global and local keywords enable us to specify whether a variable is local to a specific function or has a wider scope.

Example:

Output:

def:

The def keyword lets us create the reusable blocks of code called functions. It promotes modularity in our Python programs.

Example:

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class:

Object-oriented programming provides us with a class keyword. It is used to create classes and encapsulate the data and methods into reusable structures. Classes and objects are one of the most important concepts of object-oriented programming.

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try, except, finally:

The try, except, and finally keywords are used in the exception handling. These keywords help in easy error management and allow us to anticipate and respond to unexpected issues present in our code.

Example:

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import, from, as:

We use these keywords in modules and packages. These keywords enable us to incorporate external functionality into your code seamlessly.

Example:

Output:

We have some more keywords in Python, so we can write a program to get the list of all the Python keywords. We can print the list using the kwlist() as:

Output:

Deprecated Python Keywords

As Python has developed over the years, some of the most useful keywords become deprecated, making way for more efficient alternatives. In this section, we will look into the deprecated keywords of Python – such as the former print and exec keywords. Let us explore the reasons behind their deprecation and the alternatives that have taken their place today.

The Former print Keyword

Let's start the discussion with the former print keyword. Historically, print used to serve as the go-to function for displaying output on the console. However, as Python developed, the print function transformed into a more versatile and feature-rich print() function. By using the print() function, developers can now use additional formatting options, making their code more expressive and readable.

The Former exec Keyword

Next on the list of deprecated keywords is the former exec keyword. It once played a vital role in executing dynamic Python code. However, as Python developed, the security concerns and code maintainability issues prompted the deprecation of exec in favour of more secure alternatives. The exec() function is still available, but its use is not recommended due to potential security vulnerabilities associated with executing arbitrary code.

To adapt to these changes, developers are encouraged to replace instances of the former print and exec keywords with their modern alternatives. Developers can use the print() function which allows for more flexibility in formatting output, while opting for alternatives to exec() promotes code security and maintainability.