For Loop in Python

Last Updated: 13th December, 2023

Overview:

The for Loop in Python emphasizes over and navigates through a sequence (list, tuple, string) or other iterable objects. In other words, it  rehashes the body of the Loop for each item within the sequence. More particularly, a for Loop permits you to execute a piece of code  numerous times and is convenient after you have a piece of code that you need to rehash "n" a number of times.

Why do we use a For loop in Python?

For loops in Python are utilized when we need to execute a piece of code over and over for a fixed number of times or to repeat through a sequence of elements like lists or tuples. The For Loop could be a handy tool in Python, making it simple to execute a set of statements numerous times. It's also very flexible and can be utilized to achieve a wide range of errands, from printing out a list of numbers to iterating through complex data structures 📊.

📃Ready to utilize the Loop to perform an activity on each element within the sequence, such as printing out a list of names or including up a set of numbers. One of the foremost common use cases for a For Loop is when we need to repeat through a list or tuple. Circles are too valuable when we need to repeat through the keys or values of a dictionary.

Another advantage of employing a For circle is that it can be clearer than a whereas circle, particularly when emphasizing through a grouping. Circles can be combined with other control stream articulations, like if-else articulations, to make more complex programs.

By and large, the For circle is a fundamental apparatus in Python programming that can offer assistance to make your code more proficient, readable, and powerful.

Importance of using For Loop?

Loops are priceless for emphasizing data collection and performing complex operations on their elements. They can be utilized to search for and replace text in strings, filter and change lists, and much more. Since loops prepare elements in a sequence one by one, they can iterate over entire datasets in a single pass, avoiding the ought to load the whole dataset into memory at once. 💻

The for Loop's basic syntax and flexibility make it a principal portion of any Python programmer's toolkit. Whether you wish to execute a block of code a settled number of times or emphasize all the items in a list, tuple, dictionary, or another container, the for Loop has you secured. It could be a key apparatus for efficiency and a portal to more progressed programming techniques in Python.

Syntax of for loop in Python:

Let's explore for loops by examining the syntax and structure of a basic

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Example:

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• This code uses a for Loop to iterate through a list of numbers and print each one.
• The Loop specifies "number" as the iteration variable, referencing each item in the list.
• The Loop executes the code within it for each list item.
• Here, the code prints the iteration variable's value.

How does a for loop work in Python?

We should have a solid grasp of Python iterators to comprehend how for loops operate inside. You must understand the distinction between an iterator and an iterable. Let's look at these terms first.

• Iterable:
  • A Python object with the getitem() or iter() methods are defined. It can be looped over at a higher level if anything is iterable. Something must have the iter() function if it is iterable or can be looped over. Iterables include lists, tuples, dictionaries, sets, and strings.
• Iterator:
  • An iterator is a Python object with a state that allows it to keep track of its location during iterations. Also, the iterator has the next() function provided, which aids in retrieving successive elements stored in the iterable one after the other.

Python uses for loops to traverse through any iterable objects (For example, list, tuple, dictionary, set, or string).

Range() Function:

A for loop iterates over a list of numbers. The code inside the Loop is executed once for each number, assigning the current number to a variable for use within the Loop. As Python runs the for Loop, it keeps track of the number of iterations completed. With each iteration, the loop variable is updated. The Loop continues until all numbers in the specified range have been iterated. When all iterations are complete, Python exits the Loop and resumes the code called it.

Ways in which range function can be used:

• range(): It is a built-in function in Python that returns a number sequence.
• range(stop) : Creates a sequence of numbers from 0 up to the given number, not including the given number. For example, range(5) would create a sequence of numbers from 0 to 4.
• range(start, stop): Creates a sequence of numbers from the given start number up to the given stop number, not including the given stop number. For example, range(5, 10) would create a sequence of numbers from 5 to 9.
• range(start, increment, stop): Creates a sequence of numbers from the given start number up to the given stop number, incrementing the numbers by the given increment. For example, range(6, 2, 21) would create a sequence of numbers from 6 to 19, incrementing the numbers by 2.

Using an Else Statement with a Python For Loop

A Python for Loop with an else statement executes a block of code multiple times, and the else statement runs after the Loop finishes all iterations. The else statement can be used with a break statement to change the flow of a loop. For example, if you are iterating through a list and find a value that meets a specific condition, you can break out of the Loop and execute the else statement.

The else statement will execute once the Loop finishes all of its iterations, which is useful when you want to perform an action after the Loop exits normally. However, if the Loop is terminated early with a break statement, the else block is skipped.

Using break and else together in a for Loop gives you more control over the flow of your program. This construct provides a way to handle the Loop exiting normally versus prematurely, offering a flexible and powerful approach to looping with more advanced logic and flow control in your code.

How to go through a string in Python

The characters are contained in an iterable object called a string. We can loop through a string in Python. Despite the fact that strings cannot be changed, we may manipulate the characters to get the desired outcome.

The code sample below shows the approaches mentioned above. Python's for Loop may be used to iterate through the text in a variety of ways.

1. Method 1: Until the string is exhausted, we can iterate it character by character. Every time the for loop iterates, it selects one letter from the string, puts it in the character variable, and prints it.
2. Method 2: Using indexing is another technique for iterating through the text. We may use the range() method we have already seen because indexing begins at 0. The stop value, which serves as the Loop's end value, will be sent as an input to the range() method.
3. Method 3: The enumerate() function provides another means of iterating over the string. The string is sent as an input to the enumerate() function, which produces a key-value pair. The value of the matching letter in the string and the key, often the index number. Other numbers may also be used as a counter for the key, with the starting number being given as an input.

Example:

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The above code will loop through the string "Hello, Future Data Scientist!" and print out each letter of the string on a line by itself. The for Loop is used to iterate through each letter of the string, and the print statement prints out the letter that the Loop is currently on.

Python Nested Loops

Nested loops are loops that are within other loops. In Python, you can use nested loops to iterate through items in lists and dictionaries. Here's an example of a nested loop in Python:

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This code iterates through a list of lists and prints out each item. It uses a logical operator (len(lst) > 0) to ensure that the Loop only iterates through lists that have more than zero items and a relational operator (item != 0) to ensure that the Loop only prints out items that are not equal to zero.

Conclusion:

Overall, for loops are a fundamental part of many programming languages and a tool, all developers should understand thoroughly. Snega has made a good step  by investigating the syntax and structure of for loops. With practice, Snega will become proficient  in implementing for loops to solve a variety of programming problems.

Key takeaways:

1. A For Loop executes a set of instructions repeatedly.
2. A for Loop needs a starting point, ending point, and increment to determine how many times it will run.
3. For loops, iterate over a collection of data like arrays or lists.
4. For loops are useful for performing operations on multiple data points or counting over a range of numbers.
5. For loops can be nested to create more complex iterations.

Quiz:

1. What type of looping statement allows you to repeat a section of code until a certain condition is met? 
   1. while loop 
   2. for loop 
   3. if statement 
   4. switch statement

Answer: B. for loop

2. What looping statement allows you to repeat a section of code a predetermined number of times? 
   1. while loop 
   2. for loop 
   3. if statement 
   4. switch statement

Answer: B. for loop

3. What looping statement allows you to repeat a section of code a predetermined number of times? 
   1. while loop 
   2. for loop  
   3. if statement 
   4. switch statement

Answer: B. for loop

4. What is the output of the following code?

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a. [2, 4, 6, 8] 

b. [1, 2, 3, 4] 

c. [4, 8, 12, 16] 

d. None of the above

Answer: A [2, 4, 6, 8]