Glossary

5.2 For loop

2 min read•june 24, 2024

loops are powerful tools Python, allowing you to iterate through sequences like lists, strings, and ranges. They simplify repetitive tasks by executing a block of code for each item in a , making your programs more efficient and readable.

The function works hand-in-hand with for loops, generating number sequences for . For loops are versatile, working with various data types and performing tasks like calculations, finding values, and modifying elements based on conditions.

Iteration with for loops

Implement a for loop to iterate through a sequence of elements

Top images from around the web for Implement a for loop to iterate through a sequence of elements

  • Can anyone explain me Python for loop (or iteration) algorithm - Stack Overflow View original

    Is this image relevant?

  • performance - Fastest possible way to iterate through specific list in python - Stack Overflow View original

    Is this image relevant?

  • Can anyone explain me Python for loop (or iteration) algorithm - Stack Overflow View original

    Is this image relevant?

1 of 3

Top images from around the web for Implement a for loop to iterate through a sequence of elements

  • Can anyone explain me Python for loop (or iteration) algorithm - Stack Overflow View original

    Is this image relevant?

  • performance - Fastest possible way to iterate through specific list in python - Stack Overflow View original

    Is this image relevant?

  • Can anyone explain me Python for loop (or iteration) algorithm - Stack Overflow View original

    Is this image relevant?

1 of 3
  • For loops enable iterating over a sequence of elements (lists, tuples, strings, or other objects)
  • syntax: 
    for variable in sequence:
    • variable
      (also known as the ) takes on each value in the 
      sequence
      one at a time
    • Code block under the for loop () executes for each value of 
      variable
  • Iterating over a example: 
    fruits = ['apple', 'banana', 'cherry']
for fruit in fruits:
    print(fruit)
    Output: 
    apple
banana
cherry

Range function for sequences

  • range()
    function generates a sequence of numbers
    • Syntax: 
      range(start, stop, step)
      • start
        : Starting number of the sequence (inclusive, default 0)
      • stop
        : Ending number of the sequence (exclusive)
      • step
        : Increment between each number (default 1)
  • range()
    examples: 
    • range(5)
      : Generates numbers 0 to 4 (0, 1, 2, 3, 4)
    • range(1, 6)
      : Generates numbers 1 to 5 (1, 2, 3, 4, 5)
    • range(1, 10, 2)
      : Generates odd numbers 1 to 9 (1, 3, 5, 7, 9)
  • Using 
    range()
    with for loops: 
    for i in range(5):
    print(i)
    Output: 
    0
1
2
3
4

For loops across data types

  • For loops work with various data types:
    • Lists: 
      numbers = [1, 2, 3, 4, 5]
for num in numbers:
    print(num ** 2)
      Output: 1, 4, 9, 16, 25
    • Strings: 
      name = "John"
for char in name:
    print(char)
      Output: J, o, h, n
    • Dictionaries (iterating over keys): 
      person = {"name": "Alice", "age": 25, "city": "New York"}
for key in person:
    print(key)
      Output: name, age, city
  • For loops perform repetitive tasks:
    1. Calculating sum or product of a list of numbers
    2. Finding maximum or minimum value in a list
    3. Counting occurrences of specific elements in a list
    4. Modifying elements in a list based on conditions

Loop Control Flow and Structure

  • determines how the program executes the loop
  • The is the object that produces the next item in the sequence
  • Proper is crucial for defining the loop body and maintaining correct execution
  • The sequence is the iterable object being looped over (e.g., list, string, or range)

Key Terms to Review (28)

Break: A break statement in Python is used to exit a loop prematurely when a certain condition is met. It immediately stops the execution of the innermost loop and transfers control to the statement following that loop.
Break: The 'break' statement is a control flow statement in programming that allows a loop to be terminated prematurely, exiting the loop immediately. It is a powerful tool that provides flexibility and control over the execution of loops in various programming constructs.
Container: A container in Python is an object that holds and organizes multiple elements, often of the same type, such as lists, tuples, dictionaries, and sets. Containers are frequently used in loops to iterate over their elements.
Continue: The 'continue' statement is a control flow statement in programming that allows a loop to skip the current iteration and move on to the next one, effectively continuing the loop's execution from the next iteration. It is commonly used in the context of various loop structures, including while loops, for loops, and nested loops, to selectively bypass certain iterations based on specific conditions.
Dictionary: A dictionary in Python is a collection of key-value pairs where each key is unique. It allows for efficient data retrieval based on the keys.
Dictionary: A dictionary in Python is an unordered collection of key-value pairs, where each key is unique and is associated with a corresponding value. Dictionaries provide a flexible and efficient way to store and retrieve data, making them a fundamental data structure in the language.
Enumerate(): The 'enumerate()' function is a built-in Python function that adds a counter to an iterable object, such as a list, string, or tuple. It returns an enumerate object, which is an iterator that produces tuples containing a count (from start, which defaults to 0) and the values obtained from iterating over the sequence.
Escape sequence: An escape sequence is a series of characters used to represent special characters in a string. It typically begins with a backslash followed by one or more characters.
For: The 'for' keyword in programming is used to create loops that iterate over a sequence, such as a list or a string. This allows you to execute a block of code multiple times, making it easier to work with collections of data. The 'for' loop can simplify tasks like processing items in a list, executing repetitive calculations, or transforming data through iterations, which can enhance code efficiency and readability.
For loop: A for loop is a control flow statement that iterates over a sequence (such as a list, tuple, or string) and executes a block of code for each item in the sequence. It is commonly used to repeat actions a specific number of times or to traverse data structures.
In: The term 'in' is a preposition that is used to indicate location, time, or inclusion within a specific context. It is a fundamental part of the English language and plays a crucial role in various programming concepts, including string manipulation, list operations, dictionary usage, and control flow structures.
Indentation: Indentation refers to the consistent spacing or alignment of code elements, typically achieved through the use of whitespace characters like spaces or tabs. It is a fundamental aspect of code formatting that enhances readability and helps convey the logical structure of a program.
Iterable: An iterable is an object that can be iterated over, meaning it can be used in a loop or other sequence-based operations. Iterables are fundamental to many programming concepts, including strings, tuples, lists, and more.
Iteration: Iteration is the process of repeating a set of instructions or operations multiple times in a computer program or algorithm. It is a fundamental concept in programming that allows for the execution of a block of code repeatedly until a specific condition is met.
Iterator: An iterator is a programming construct that allows you to traverse through a sequence of elements, such as the items in a list or the characters in a string, one at a time. It provides a standardized way to access the elements of a collection without exposing the underlying implementation details.
List: A list in Python is an ordered collection of items, where each item can be of a different data type. Lists are one of the most fundamental and versatile data structures in the Python programming language, allowing you to store and manipulate multiple values in a single variable.
List comprehension: List comprehension is a concise way to create lists in Python using a single line of code. It consists of brackets containing an expression followed by a for clause and optionally, one or more if clauses.
List Comprehension: List comprehension is a concise and efficient way to create new lists in Python by applying a transformation or condition to each element of an existing list. It allows for the creation of lists in a single, compact expression, making code more readable and reducing the need for traditional looping structures.
Loop Body: The loop body refers to the set of instructions or statements that are executed repeatedly within a loop construct, such as a while loop or a for loop, until the loop's termination condition is met. It is the core of the looping mechanism, where the actual operations or computations take place during each iteration of the loop.
Loop Control Flow: Loop control flow refers to the mechanisms that govern the execution and behavior of loops in programming. It determines how a loop iterates, when it starts, when it ends, and how the flow of control is managed within the loop.
Loop Variable: A loop variable is a variable that is used to control the number of iterations or repetitions in a loop. It is a key component in both while loops and for loops, as it determines when the loop should stop executing.
Nested Loops: Nested loops refer to the concept of placing one loop structure (either a for loop or a while loop) inside another loop structure. This allows for the execution of multiple iterations within a single iteration of the outer loop, enabling complex and multidimensional data processing.
Pass: The 'pass' statement in Python is a placeholder that does nothing. It is used as a way to indicate that a section of code should do nothing, often used as a temporary measure or when a statement is required syntactically but no action is needed. It is a way to create an empty block of code, allowing the program to continue executing without errors.
Pass-by-object-reference: Pass-by-object-reference is a method of passing arguments to functions where the reference (or address) of the object is passed, not the actual object itself. This means changes made to the object within the function affect the original object outside the function.
Range(): range() is a built-in Python function used to generate a sequence of numbers. It is commonly used in for loops to iterate over a series of values.
Sequence: A sequence is an ordered arrangement of elements, such as numbers, letters, or objects, that follow a specific pattern or order. This concept is fundamental in various areas of computer science and mathematics, including programming, data structures, and algorithms.
Time Complexity: Time complexity is a measure of how long an algorithm or a computer program will take to run as a function of the size of its input. It is a crucial concept in computer science that helps analyze the efficiency and scalability of algorithms and programs.
Zip(): The zip() function in Python is a built-in function that takes two or more iterables (such as lists, tuples, or strings) and returns an iterator of tuples, where each tuple contains the corresponding elements from each iterable. It is particularly useful for looping through multiple iterables simultaneously and pairing their elements together.
© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.
Back
Practice QuizGlossary
Practice QuizGlossary
Next guide