Table of Contents
Introduction
Welcome to the world of Python programming! In this tutorial, we’ll explore the versatile “for” loop. Whether you’re a beginner or an experienced programmer, understanding the various use cases of the “for” loop is essential. We’ll cover everything you need to know, from iterating over sequences to working with dictionaries and even combining the “for” loop with conditional statements. Let’s dive in and unlock the power of the “for” loop!
Iterating over Sequences
The most common use of the “for” loop is to iterate over sequences like lists, tuples, and strings. Here’s an example of iterating over a list:
fruits = [“apple”, “banana”, “orange”]
for fruit in fruits:
print(fruit)
Output:
apple
banana
orange
Iterating over a String
message = “Hello, World!”
for char in message:
print(char)
Output
H
e
l
l
o
,
W
o
r
l
d
!
Skipping Iterations with “continue”
numbers = [1, 2, 3, 4, 5, 6]
for num in numbers:
if num % 2 == 0:
continue
print(num)
Output
1
3
5
Iterating over a Range with a Step
for i in range(1, 11, 2):
print(i)
Output
1
3
5
7
9
Iterating over a List of Lists
matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
for row in matrix:
for num in row:
print(num)
Output
1
2
3
4
5
6
7
8
9
Range Function
The range() function in Python generates a sequence of numbers. It is commonly used in conjunction with the for loop to iterate over a specific range of values. The range() function can be called with one, two, or three arguments, depending on the desired behavior.
Syntax
range(stop)
range(start, stop)
range(start, stop, step)
Parameters
start(optional): The starting value of the sequence (inclusive). If not specified, the default is 0.stop(required): The ending value of the sequence (exclusive). The sequence will generate values up to, but not including, this value.step(optional): The increment between each number in the sequence. If not specified, the default is 1.
Using range() with one argument:
for i in range(5):
print(i)
Output
0
1
2
3
4
Using range() with two arguments:
for i in range(2, 6):
print(i)
Output
2
3
4
5
Using range() with three arguments:
for i in range(1, 10, 2):
print(i)
Output
1
3
5
7
9
In this case, the range(1, 10, 2) generates a sequence starting from 1, incrementing by 2 at each step, and stopping before 10.
The range() function is particularly useful for creating loops that iterate a specific number of times or for generating sequences of numbers within a defined range. By adjusting the start, stop, and step parameters, you have fine control over the values produced by the range() function.
Using the “range” Function
The “range” function generates a sequence of numbers, often used with the “for” loop. Here’s an example of printing numbers from 1 to 5:
for num in range(1, 6):
print(num)
Output
1
2
3
4
5
Summing Elements of a List
The “for” loop can be used to iterate over a list and calculate the sum of its elements. Here’s an example:
numbers = [1, 2, 3, 4, 5]
sum = 0
for num in numbers:
sum += num
print(“Sum:”, sum)
Output
Sum: 15
Finding the Maximum or Minimum Element in a List
The “for” loop can be used to find the maximum or minimum element in a list. Here’s an example of finding the maximum element:
numbers = [3, 7, 1, 9, 5]
max_num = numbers[0]
for num in numbers:
if num > max_num:
max_num = num
print(“Maximum Number:”, max_num)
Output
Maximum Number: 9
Counting the Occurrences of an Element in a List
The “for” loop can be used to count the occurrences of a specific element in a list. Here’s an example:
numbers = [1, 2, 1, 3, 4, 1]
target = 1
count = 0
for num in numbers:
if num == target:
count += 1
print(“Count of”, target, “:”, count)
Output
Count of 1: 3
Iterating over Dictionaries
The “for” loop can also iterate over dictionaries, allowing you to access both keys and values. Here’s an example:
student_grades = {“Alice”: 85, “Bob”: 92, “Charlie”: 78}
for name, grade in student_grades.items():
print(name, “scored”, grade)
Output
Alice scored 85
Bob scored 92
Charlie scored 78
In this example, the “for” loop iterates over each key-value pair in the student_grades dictionary using the “items()” method, and prints the name and corresponding grade.
Combining the “for” Loop with Conditional Statements
The “for” loop can be combined with conditional statements to perform selective iterations. Here’s an example of printing only even numbers from 1 to 10:
for num in range(1, 11):
if num % 2 == 0:
print(num)
Output
2
4
6
8
10
Conclusion
Congratulations! You’ve now mastered the “for” loop in Python. You’ve learned how to iterate over sequences, use the “range” function, work with dictionaries, and combine the “for” loop with conditional statements. The “for” loop is a powerful tool for repetitive operations and is widely used in Python programming. Keep practicing and exploring different scenarios to enhance your coding skills. Happy looping!