Loops hold significant importance in Python. They enable the execution of a code block multiple times without the necessity to rewrite it repeatedly. They prove beneficial for evaluating conditions, handling sequences, and automating tasks that are repetitive. Python provides various loop types, each serving distinct purposes. Moreover, loops can be nested within one another, allowing the simultaneous management of multiple sequences and facilitating intricate operations. Understanding which loop to employ and at what moment is essential. This comprehension enhances code readability and improves runtime efficiency. In this article, you will gain insights into loops in Python, including their varieties, syntax, and detailed examples for each.
Loops are fundamental in Python, as they facilitate iteration over a set of conditions until they are fulfilled. This functionality means tasks can be repeated without needing to rewrite the code. Python has two primary loop types: for loops, which are ideal when the number of iterations is known (or when looping through elements of a list, string, or other collections), and while loops that persist in execution as long as a specified condition remains true. Employing loops in Python streamlines the handling of repetitive tasks and enhances the program’s conciseness and effectiveness.
Features of loops in Python
Automatic Iteration: Loops facilitate seamless movement through items in a sequence without requiring manual indexing.
Break and Continue: Loops allow manipulation of the execution flow via the break statement, which can terminate the loop early, and the continue statement, which enables skipping the current iteration and advancing to the next.
Code Simplification: Loops diminish code redundancy, contributing to faster and more efficient programs.
Control Flexibility: You can adjust the execution frequency of a loop based on certain conditions or a counter.
Infinite Capability: There is potential for infinite loops using a while True structure, which must be manually exited or terminated using a break statement.
Range() Compatibility: For loops integrate well with the Python function range() to repeat tasks a specified number of times.
Else with Loops: Python permits the inclusion of an optional else clause that executes after a loop has completed normally.
Enhance Your Python Proficiency – Begin Your Journey Today!
Enroll now to acquire sought-after Python skills and distinguish yourself in the job market.
Now, let’s delve into the various types of loops and how each operates.
1. For loop in Python
A for loop is employed to traverse each item within a sequence. It executes a block of code individually for each item, making it suitable for tasks demanding consistent repetitions over a predetermined number of times.
Flowchart:
Syntax:
for iterating_var in sequence:
statement(s)
Example:
Python
Code Copied!
“““html
var isMobile = window.innerWidth “);
editor62457.setValue(decodedContent); // Set the initial text
editor62457.clearSelection();
editor62457.setOptions({
maxLines: Infinity
});
function decodeHTML62457(input) {
var doc = new DOMParser().parseFromString(input, “text/html”);
return doc.documentElement.textContent;
}
// Function to copy code to clipboard
function copyCodeToClipboard62457() {
const code = editor62457.getValue(); // Retrieve code from the editor
navigator.clipboard.writeText(code).then(() => {
jQuery(“.maineditor62457 .copymessage”).show();
setTimeout(function() {
jQuery(“.maineditor62457 .copymessage”).hide();
}, 2000);
}).catch(err => {
console.error(“Error copying code: “, err);
});
}
function runCode62457() {
var code = editor62457.getSession().getValue();
jQuery.ajax({
url: “https://intellipaat.com/blog/wp-admin/admin-ajax.php”,
type: “post”,
data: {
language: “python”,
code: code,
cmd_line_args: “”,
variablenames: “”,
action:”compilerajax”
},
success: function(response) {
var myArray = response.split(“~”);
var data = myArray[1];
jQuery(“.output62457”).html(“
"+data+"");
jQuery(".maineditor62457 .code-editor-output").show();
jQuery("#runBtn62457 i.run-code").hide();
}
});
}
function closeoutput62457() {
jQuery(".maineditor62457 .code-editor-output").hide();
}
// Attach event listeners to the buttons
document.getElementById("copyBtn62457").addEventListener("click", copyCodeToClipboard62457);
document.getElementById("runBtn62457").addEventListener("click", runCode62457);
document.getElementById("closeoutputBtn62457").addEventListener("click", closeoutput62457);
Output:
Explanation: In this instance, the for loop is utilized to iterate through each course in the list and display a notification to study the course at Intellipaat.
Benefits of Employing a for Loop in Python:
Facilitates the traversal of elements within a list or other sequences with ease.
Simplifies the code, enhancing readability.
Automatically manages counting or progression to subsequent elements.
Drawbacks of Utilizing a for Loop in Python:
Provides limited control to terminate the loop prematurely.
Not suitable for situations requiring indefinite iterations.
Not ideal when the condition is more intricate.
Incorporating the else statement with a For Loop in Python
The else statement following a for loop executes solely when all items are processed by the loop without any interruptions. If the loop is terminated prematurely using a break statement, the else block will not execute.
Syntax:
for item in sequence:
statement(s)
else:
statement(s)
Example:
Python
Code Copied!
var isMobile = window.innerWidth “);
editor49549.setValue(decodedContent); // Set the default text
editor49549.clearSelection();
editor49549.setOptions({
maxLines: Infinity
});
function decodeHTML49549(input) {
var doc = new DOMParser().parseFromString(input, “text/html”);
return doc.documentElement.textContent;
}
// Function to copy code to clipboard
function copyCodeToClipboard49549() {
const code = editor49549.getValue(); // Retrieve code from the editor
navigator.clipboard.writeText(code).then(() => {
jQuery(“.maineditor49549 .copymessage”).show();
setTimeout(function() {
jQuery(“.maineditor49549 .copymessage”).hide();
}, 2000);
}).catch(err => {
console.error(“Error copying code: “, err);
});
}
function runCode49549() {
var code = editor49549.getSession().getValue();
jQuery.ajax({
url: “https://intellipaat.com/blog/wp-admin/admin-ajax.php”,
type: “post”,
data: {
language: “python”,
code: code,
cmd_line_args: “”,
variablenames: “”,
action:”compilerajax”
},
success: function(response) {
var myArray = response.split(“~”);
var data = myArray[1];
jQuery(“.output49549”).html(“
"+data+"");
jQuery(".maineditor49549 .code-editor-output").show();
jQuery("#runBtn49549 i.run-code").hide();
}
});
}
``````html
.code-editor-output").show();
jQuery("#runBtn49549 i.run-code").hide();
}
})
}
function closeOutput49549() {
var code = editor49549.getSession().getValue();
jQuery(".maineditor49549 .code-editor-output").hide();
}
// Attach event listeners to the buttons
document.getElementById("copyBtn49549").addEventListener("click", copyCodeToClipboard49549);
document.getElementById("runBtn49549").addEventListener("click", runCode49549);
document.getElementById("closeoutputBtn49549").addEventListener("click", closeOutput49549);
Output:
Explanation: In this instance, the for loop iterates through all courses. Once all courses are completed, the else block executes, displaying the completion notification.
2. While Loop in Python
A while loop in Python continues executing a series of instructions as long as a specific condition is met. It is particularly useful when the number of repetitions required is uncertain. The loop halts when the condition evaluates to false. This is advantageous for situations such as awaiting user input or validating values.
Flowchart:
Syntax:
while condition: statement(s)
Example:
Python
Code Copied!
var isMobile = window.innerWidth ");
editor40572.setValue(decodedContent); // Set the default text
editor40572.clearSelection();
editor40572.setOptions({
maxLines: Infinity
});
function decodeHTML40572(input) {
var doc = new DOMParser().parseFromString(input, "text/html");
return doc.documentElement.textContent;
}
// Function to copy code to clipboard
function copyCodeToClipboard40572() {
const code = editor40572.getValue(); // Retrieve code from the editor
navigator.clipboard.writeText(code).then(() => {
// alert("Code copied to clipboard!");
data: {
language: "python",
code: code,
cmd_line_args: "",
variablenames: "",
action:"compilerajax"
},
success: function(response) {
var myArray = response.split("~");
var data = myArray[1];
jQuery(".output40572").html("
"+data+"");
jQuery(".maineditor40572 .code-editor-output").show();
jQuery("#runBtn40572 i.run-code").hide();
}
})
}
function closeOutput40572() {
var code = editor40572.getSession().getValue();
jQuery(".maineditor40572 .code-editor-output").hide();
}
// Attach event listeners to the buttons
document.getElementById("copyBtn40572").addEventListener("click", copyCodeToClipboard40572);
document.getElementById("runBtn40572").addEventListener("click", runCode40572);
document.getElementById("closeoutputBtn40572").addEventListener("click", closeOutput40572);
Output:
Explanation: In this situation, the loop continues until the study hours total 3.
Advantages of Utilizing a While Loop in Python:
It’s applicable when the number of iterations is uncertain.
It can be used for continuous value checking.
It’s useful when user input is required.
Disadvantages of Utilizing a While Loop in Python:
It may enter an infinite loop if a termination condition is not specified.
Diagnosing and correcting issues can be challenging.
It must be updated within the loop to ensure termination.
Using the else statement with a While Loop in Python
The else clause following a while loop executes solely when the loop concludes naturally. If the loop is prematurely terminated using a break statement, the else block will not execute.
Syntax:
while condition: statement(s) else: statement(s)
Example:
Python
Code Duplicated!
var isMobile = window.innerWidth “);
editor94019.setValue(decodedContent); // Set the default text
editor94019.clearSelection();
editor94019.setOptions({
maxLines: Infinity
});
function decodeHTML94019(input) {
var doc = new DOMParser().parseFromString(input, “text/html”);
return doc.documentElement.textContent;
}
// Function to copy code to clipboard
function copyCodeToClipboard94019() {
const code = editor94019.getValue(); // Acquire code from the editor
navigator.clipboard.writeText(code).then(() => {
// alert(“Code placed on clipboard!”);
jQuery(“.maineditor94019 .copymessage”).show();
setTimeout(function() {
jQuery(“.maineditor94019 .copymessage”).hide();
}, 2000);
}).catch(err => {
console.error(“Issue with copying code: “, err);
});
}
function runCode94019() {
var code = editor94019.getSession().getValue();
data: {
language: “python”,
code: code,
cmd_line_args: “”,
variablenames: “”,
action:”compilerajax”
},
success: function(response) {
var myArray = response.split(“~”);
var data = myArray[1];
jQuery(“.output94019”).html(“
"+data+"");
jQuery(".maineditor94019 .code-editor-output").show();
jQuery("#runBtn94019 i.run-code").hide();
}
})
}
function closeoutput94019() {
var code = editor94019.getSession().getValue();
jQuery(".maineditor94019 .code-editor-output").hide();
}
// Attach event listeners to buttons
document.getElementById("copyBtn94019").addEventListener("click", copyCodeToClipboard94019);
document.getElementById("runBtn94019").addEventListener("click", runCode94019);
document.getElementById("closeoutputBtn94019").addEventListener("click", closeoutput94019);
Output:
Explanation: The loop operates for 5 days. Once all days are complete, the else segment executes to commemorate the achievement.
3. Nested Loop in Python
A nested loop is a loop situated within another loop, enabling you to manage data that consists of lists within lists. The inner loop processes its elements entirely for each iteration of the outer loop. It is immensely beneficial for dealing with table-like structures or bundling related data items together.
Syntax:
for i in outer_sequence: for j in inner_sequence: statement(s)
Example:
Python
Code Duplicated!
var isMobile = window.innerWidth ");
editor93262.setValue(decodedContent); // Set the default text
editor93262.clearSelection();
editor93262.setOptions({
maxLines: Infinity
});
function decodeHTML93262(input) {
var doc = new DOMParser().parseFromString(input, "text/html");
return doc.documentElement.textContent;
}
// Function to copy code to clipboard
function copyCodeToClipboard93262() {
const code = editor93262.getValue(); // Acquire code from the editor
navigator.clipboard.writeText(code).then(() => {
// alert("Code placed on clipboard!");
jQuery(".maineditor93262 .copymessage").show();
setTimeout(function() {
jQuery(".maineditor93262 .copymessage").hide();
}, 2000);
}).catch(err => {
console.error("Issue with copying code: ", err);
});
}
function runCode93262() {
var code = editor93262.getSession().getValue();
function closeOutput93262() {
var code = editor93262.getSession().getValue();
jQuery(".maineditor93262 .code-editor-output").hide();
}
// Attach event listeners to the buttons
document.getElementById("copyBtn93262").addEventListener("click", copyCodeToClipboard93262);
document.getElementById("runBtn93262").addEventListener("click", runCode93262);
document.getElementById("closeoutputBtn93262").addEventListener("click", closeOutput93262);
Output:
Explanation: In this case, the loop executes once and halts using break, preventing it from entering an infinite cycle.
Benefits of Using Nested Loops in Python:
It can facilitate the creation of pairs or groups of data.
It can be utilized when one loop relies on another.
It allows for repeated tasks for every combination of two sets of data.
Drawbacks of Using Nested Loops in Python:
The code may become larger and harder to read.
Identifying errors can be difficult if too many loops are present.
Performance can diminish with a larger number of items, as each inner loop must run for every item in the outer loop.
Using the else clause with a Nested Loop in Python
In nested loops, an else clause following the inner loop executes only if the inner loop does not exit early, completing all iterations. An else clause linked to the outer loop only runs if the outer loop completes all iterations and exits naturally.
Syntax:
for outer_item in outer_sequence: for inner_item in inner_sequence: statement(s) else: statement(s) else: statement(s)
Example:
Python
Code Copied!
var isMobile = window.innerWidth “);
editor16303.setValue(decodedContent); // Set the initial text
editor16303.clearSelection();
editor16303.setOptions({
maxLines: Infinity
});
function decodeHTML16303(input) {
var doc = new DOMParser().parseFromString(input, “text/html”);
return doc.documentElement.textContent;
}
// Function to copy code to clipboard
function copyCodeToClipboard16303() {
const code = editor16303.getValue(); // Retrieve code from the editor
navigator.clipboard.writeText(code).then(() => {
jQuery(“.maineditor16303 .copymessage”).show();
setTimeout(function() {
jQuery(“.maineditor16303 .copymessage”).hide();
}, 2000);
}).catch(err => {
console.error(“Error copying code: “, err);
});
}
function runCode16303() {
var code = editor16303.getSession().getValue();
function closeOutput16303() {
var code = editor16303.getSession().getValue();
jQuery(“.maineditor16303 .code-editor-output”).hide();
}
// Attach event listeners to the buttons
document.getElementById(“copyBtn16303”).addEventListener(“click”, copyCodeToClipboard16303);
document.getElementById(“runBtn16303”).addEventListener(“click”, runCode16303);
document.getElementById(“closeoutputBtn16303”).addEventListener(“click”, closeOutput16303);
Output:
Explanation: In this instance, the inner loop finishes all tasks for each day and invokes the inner else. Following the conclusion of both days, the outer else executes, presenting the final message.
Endless loops in Python
An endless loop continues to operate indefinitely because its condition never evaluates to false. This can occur inadvertently or purposefully when a program is designed to run endlessly until manually terminated.
There are two varieties of endless loops in Python
Endless for loop
“““html
Endless While Loop
1. Endless For Loop in Python
An endless for loop in Python happens when the loop is set to iterate indefinitely using a specialized iterator such as itertools.cycle(). It runs until a break statement interrupts it.
Syntax:
import itertools for item in itertools.cycle(sequence): statement(s)
Illustration:
Python
Code Copied!
var isMobile = window.innerWidth “);
editor84498.setValue(decodedContent); // Set the default text
editor84498.clearSelection();
editor84498.setOptions({
maxLines: Infinity
});
function decodeHTML84498(input) {
var doc = new DOMParser().parseFromString(input, “text/html”);
return doc.documentElement.textContent;
}
// Function to copy code to clipboard
function copyCodeToClipboard84498() {
const code = editor84498.getValue(); // Get code from the editor
navigator.clipboard.writeText(code).then(() => {
// alert(“Code copied to clipboard!”);
data: {
language: “python”,
code: code,
cmd_line_args: “”,
variablenames: “”,
action:”compilerajax”
},
success: function(response) {
var myArray = response.split(“~”);
var data = myArray[1];
jQuery(“.output84498”).html(“
"+data+"");
jQuery(".maineditor84498 .code-editor-output").show();
jQuery("#runBtn84498 i.run-code").hide();
}
})
}
function closeoutput84498() {
var code = editor84498.getSession().getValue();
jQuery(".maineditor84498 .code-editor-output").hide();
}
// Attach event listeners to the buttons
document.getElementById("copyBtn84498").addEventListener("click", copyCodeToClipboard84498);
document.getElementById("runBtn84498").addEventListener("click", runCode84498);
document.getElementById("closeoutputBtn84498").addEventListener("click", closeoutput84498);
Result:
Clarification: In this case, the loop repeats the sequence [1, 2, 3] infinitely. The break halts it after 6 iterations to avoid continuous execution.
2. Endless While Loop in Python
An endless while loop takes place when the loop's condition is perpetually true, resulting in the loop executing indefinitely. The loop halts only when a break statement is used or if the program is manually terminated.
Syntax:
while True: statement(s)
Illustration:
Python
Code Copied!
var isMobile = window.innerWidth ");
editor49350.setValue(decodedContent); // Set the default text
editor49350.clearSelection();
editor49350.setOptions({
maxLines: Infinity
});
function decodeHTML49350(input) {
var doc = new DOMParser().parseFromString(input, "text/html");
return doc.documentElement.textContent;
}
// Function to copy code to clipboard
function copyCodeToClipboard49350() {
const code = editor49350.getValue(); // Fetch code from the editor
navigator.clipboard.writeText(code).then(() => {
// alert("Code copied to clipboard!");
function closeOutput49350() {
var code = editor49350.getSession().getValue();
jQuery(".maineditor49350 .code-editor-output").hide();
}
// Attach event listeners to the buttons
document.getElementById("copyBtn49350").addEventListener("click", copyCodeToClipboard49350);
document.getElementById("executeBtn49350").addEventListener("click", executeCode49350);
document.getElementById("closeOutputBtn49350").addEventListener("click", closeOutput49350);
Result:
Clarification: In this scenario, the while loop continues indefinitely as the condition remains True. The break statement halts the loop after 5 iterations.
Performance Comparison: For Loop vs While Loop vs Nested Loop
Characteristic
For Loop
While Loop
Nested Loop
Objective
For iterating through each item in a sequence
For iterating as long as a condition holds true
For executing one loop within another to tackle intricate structures
Condition Kind
Depends on items in a range or collection
Depends on a logical condition
Both inner and outer loops have their own conditions
When to Apply
When the repeat count is predetermined by a condition
When the terminating condition is uncertain beforehand
Dealing with grids, tables, or paired operations
Example Scenario
Iterating over a list of course topics
Looping until a user inputs the correct information
To evaluate all combinations within a nested structure
Recommended Practices for Using Loops in Python
Utilize clear variable names: Employ descriptive names reflecting their purpose, such as count, item, or score, to enhance code readability.
Keep looping code straightforward: Incorporate only essential steps within the loop for improved clarity.
Implement break and continue: Use break for early loop termination, and continue to bypass looping steps at appropriate moments.
Ensure loop termination: Set your loop condition to guarantee it will conclude, as failing to do so can lead to an endless loop.
Using else with loops: The else statement in a loop executes solely if the loop concludes without encountering a break. This should be planned in advance.
Learn Python for Free – Start Developing Real Skills Today!
Enroll in our free course and begin mastering Python
Python loops are highly effective for repetitive tasks, controlling program flow, and minimizing the volume of code written each time. Utilizing various loop types, including while and nested loops, enables efficient task handling. Grasping the use of the else statement in conjunction with loops proves beneficial for managing exceptions, allowing code execution only when the loop completes without interruption. By applying the provided tips and strategies, you will be able to craft clear, efficient, and well-organized Python programs.
To elevate your abilities, register for our Python Training Course for practical experience. Additionally, prepare for job interviews using our Python Interview Questions designed by industry professionals.
Loops in Python – Frequently Asked Questions
Q1. What constitutes a loop in Python?
Loops function to repeat a block of code multiple times until specified conditions are fulfilled.
Q2. When should one use a for loop versus a while loop?
A for loop is suitable when iteration count is predefined, while a while loop is appropriate when iterations depend on a condition.
Q3. Is it possible to use an else block with loops?
Yes, the else segment of the code executes only if the loop concludes without invoking the break statement.
Q4. What is an infinite loop?
An infinite loop is one that perpetually continues running as its condition remains true.
Q5. Are nested loops permissible in Python?
Absolutely, a loop can be nested within another to manage multi-layered tasks.
To provide the best experiences, we use technologies like cookies to store and/or access device information. Consenting to these technologies will allow us to process data such as browsing behavior or unique IDs on this site. Not consenting or withdrawing consent, may adversely affect certain features and functions.
Functional
Always active
The technical storage or access is strictly necessary for the legitimate purpose of enabling the use of a specific service explicitly requested by the subscriber or user, or for the sole purpose of carrying out the transmission of a communication over an electronic communications network.
Preferences
The technical storage or access is necessary for the legitimate purpose of storing preferences that are not requested by the subscriber or user.
Statistics
The technical storage or access that is used exclusively for statistical purposes.The technical storage or access that is used exclusively for anonymous statistical purposes. Without a subpoena, voluntary compliance on the part of your Internet Service Provider, or additional records from a third party, information stored or retrieved for this purpose alone cannot usually be used to identify you.
Marketing
The technical storage or access is required to create user profiles to send advertising, or to track the user on a website or across several websites for similar marketing purposes.
