Introduction
In the last tutorial, you learned about Python’s core data
structures: lists, tuples, and dictionaries. Now it’s time to combine them with
loops to process collections of data. This is where Python becomes truly
powerful — you can automate repetitive tasks, analyse datasets, and build
practical mini-projects.
Step 1: Looping Through Lists
Lists are often processed
with for loops.
Code:
numbers = [10, 20, 30, 40]
for num in numbers:
print(num * 2)
Output:
20
40
60
80
Step 2: Looping Through Tuples
Tuples work the same way, but since they’re immutable, you
usually just read values.
Code:
coordinates = (2, 4, 6)
for point in coordinates:
print(point)
Output:
2
4
6
Step 3: Looping Through Dictionaries
Dictionaries are slightly different because they store
key-value pairs.
student = {
"name":
"Deepak",
"age": 30,
"course":
"Python"
}
for key, value in student.items():
print(key,
":", value)
Output:
name : Deepak
age : 30
course : Python
.items() gives both the key and value
at once.
Step 4: Nested Loops with Data Structures
You can use nested loops to process complex data.
students = [
{"name":
"Alice", "age": 22},
{"name":
"Bob", "age": 25},
{"name":
"Charlie", "age": 23}
]
for student in students:
for key, value in
student.items():
print(key,
":", value)
print("---")
Output:
name : Alice
age : 22
---
name : Bob
age : 25
---
name : Charlie
age : 23
---
Step 5: Building a Mini Project — Contact Book
Let’s create a simple contact book using a dictionary and loops.
Code:
contacts = {
"Alice":
"123-456-7890",
"Bob":
"987-654-3210",
"Charlie":
"555-666-7777"
}
print("Contact List:")
for name, phone in contacts.items():
print(f"{name}: {phone}")
Output:
Contact List:
Alice: 123-456-7890
Bob: 987-654-3210
Charlie: 555-666-7777
This is a practical example of how loops and dictionaries
work together.
Mini Exercise
Try this challenge:
·
Create a list of 5 numbers.
·
Use a loop to calculate the
square of each number.
·
Store the results in a
dictionary where the key is the number and the value is its square.
·
Print the dictionary.
Hint:
numbers = [1, 2, 3, 4, 5]
squares = {}
for num in numbers:
squares[num] = num ** 2
print(squares)
Output:
{1: 1, 2: 4, 3: 9, 4: 16, 5: 25}
Conclusion
In this tutorial, you learned how to:
·
Loop through lists, tuples,
and dictionaries
·
Use nested loops for
complex data
·
Build a simple contact book
project
·
Combine loops and data
structures for practical tasks
Loops + data structures are the engine of automation in
Python. With these tools, you can process large datasets, build applications,
and create efficient workflows.
In the next tutorial, we’ll explore Python modules and
libraries — how to import and use external code to expand your programs.