Python Data Types

Introduction

In Python, data types are the classification of data items. Data types represent the kind of value that tells what operations can be performed on a particular data. Python has several built-in data types that allow you to store and manipulate different kinds of information.

Understanding data types is fundamental to programming in Python because:

• They determine what values a variable can hold
• They define what operations can be performed on the data
• They influence how memory is allocated for your data
• They affect the performance and behavior of your code

Let's explore the different data types available in Python and how to work with them.

Basic Data Types in Python

Numbers

Python supports different numerical types:

Integers

Integers are whole numbers without a decimal point.

python

# Integer examples
x = 10
y = -5
big_number = 1234567890

print(x)       # Output: 10
print(type(x)) # Output: <class 'int'>

Floating Point Numbers

Floats are numbers with a decimal point.

python

# Float examples
pi = 3.14159
e = 2.71828
negative_float = -0.5

print(pi)       # Output: 3.14159
print(type(pi)) # Output: <class 'float'>

Complex Numbers

Complex numbers have a real and imaginary part.

python

# Complex number examples
c = 3 + 4j
print(c)       # Output: (3+4j)
print(type(c)) # Output: <class 'complex'>
print(c.real)  # Output: 3.0
print(c.imag)  # Output: 4.0

Strings

Strings are sequences of characters enclosed in quotes (single or double).

python

# String examples
name = "Python"
message = 'Hello, World!'
multiline = """This is a
multiline string"""

print(name)     # Output: Python
print(type(name)) # Output: <class 'str'>

# String operations
print(name + " Programming")  # Output: Python Programming
print(name * 3)               # Output: PythonPythonPython
print(name[0])                # Output: P (first character)
print(name[1:4])              # Output: yth (slicing)
print(len(message))           # Output: 13 (length of string)

Boolean

Booleans represent truth values: either True or False.

python

# Boolean examples
is_python_fun = True
is_coding_hard = False

print(is_python_fun)     # Output: True
print(type(is_python_fun)) # Output: <class 'bool'>

# Boolean operations
print(is_python_fun and is_coding_hard)  # Output: False
print(is_python_fun or is_coding_hard)   # Output: True
print(not is_coding_hard)                # Output: True

Sequence Types

Lists

Lists are ordered, mutable collections that can contain items of different data types.

python

# List examples
fruits = ['apple', 'banana', 'cherry']
mixed_list = [1, 'hello', 3.14, True]

print(fruits)      # Output: ['apple', 'banana', 'cherry']
print(type(fruits)) # Output: <class 'list'>

# List operations
fruits.append('orange')  # Add an item
print(fruits)  # Output: ['apple', 'banana', 'cherry', 'orange']

fruits.remove('banana')  # Remove an item
print(fruits)  # Output: ['apple', 'cherry', 'orange']

print(fruits[0])   # Output: apple (first item)
print(fruits[-1])  # Output: orange (last item)

# List slicing
print(fruits[0:2]) # Output: ['apple', 'cherry']

# List comprehension
squares = [x**2 for x in range(5)]
print(squares)  # Output: [0, 1, 4, 9, 16]

Tuples

Tuples are ordered, immutable collections that can contain items of different data types.

python

# Tuple examples
coordinates = (10, 20)
person = ('John', 30, 'New York')

print(coordinates)      # Output: (10, 20)
print(type(coordinates)) # Output: <class 'tuple'>

# Tuple operations
print(coordinates[0])   # Output: 10
print(person[1:])       # Output: (30, 'New York')

# Tuple unpacking
x, y = coordinates
print(x, y)  # Output: 10 20

# Tuples are immutable - this will cause an error
# coordinates[0] = 15  # TypeError: 'tuple' object does not support item assignment

Mapping Type

Dictionaries

Dictionaries are unordered collections of key-value pairs.

python

# Dictionary examples
student = {
    'name': 'John',
    'age': 20,
    'courses': ['Math', 'Science', 'History']
}

print(student)      # Output: {'name': 'John', 'age': 20, 'courses': ['Math', 'Science', 'History']}
print(type(student)) # Output: <class 'dict'>

# Dictionary operations
print(student['name'])  # Output: John

student['age'] = 21     # Modify value
print(student)  # Output: {'name': 'John', 'age': 21, 'courses': ['Math', 'Science', 'History']}

student['email'] = '[email protected]'  # Add new key-value pair
print(student)  # Output includes the new email

# Get method with default value
print(student.get('phone', 'Not Available'))  # Output: Not Available

# Dictionary comprehension
squares_dict = {x: x**2 for x in range(5)}
print(squares_dict)  # Output: {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

Set Types

Sets

Sets are unordered collections of unique elements.

python

# Set examples
fruits_set = {'apple', 'banana', 'cherry', 'apple'}  # Duplicate will be removed
print(fruits_set)  # Output: {'apple', 'banana', 'cherry'}
print(type(fruits_set))  # Output: <class 'set'>

# Set operations
fruits_set.add('orange')
print(fruits_set)  # Output: {'apple', 'banana', 'cherry', 'orange'}

fruits_set.remove('banana')
print(fruits_set)  # Output: {'apple', 'cherry', 'orange'}

# Set operations
set1 = {1, 2, 3, 4, 5}
set2 = {4, 5, 6, 7, 8}

print(set1.union(set2))        # Output: {1, 2, 3, 4, 5, 6, 7, 8}
print(set1.intersection(set2)) # Output: {4, 5}
print(set1.difference(set2))   # Output: {1, 2, 3}

Frozen Sets

Frozen sets are immutable versions of sets.

python

# Frozen set example
frozen = frozenset([1, 2, 3, 4])
print(frozen)  # Output: frozenset({1, 2, 3, 4})
print(type(frozen))  # Output: <class 'frozenset'>

# Frozen sets are immutable - this will cause an error
# frozen.add(5)  # AttributeError: 'frozenset' object has no attribute 'add'

None Type

Python has a special data type called None which represents the absence of a value.

python

# None example
result = None
print(result)  # Output: None
print(type(result))  # Output: <class 'NoneType'>

# Common use case
def function_without_return():
    pass  # Function does nothing

value = function_without_return()
print(value)  # Output: None

Type Conversion

Python allows you to convert between different data types using built-in functions.

python

# Type conversion examples
# Converting to int
x = int(3.14)
print(x)  # Output: 3

y = int("10")
print(y)  # Output: 10

# Converting to float
a = float(5)
print(a)  # Output: 5.0

b = float("3.14")
print(b)  # Output: 3.14

# Converting to string
c = str(10)
print(c)  # Output: "10"

d = str(3.14)
print(d)  # Output: "3.14"

# Converting to list, tuple, set
string = "hello"
print(list(string))  # Output: ['h', 'e', 'l', 'l', 'o']
print(tuple(string))  # Output: ('h', 'e', 'l', 'l', 'o')
print(set(string))    # Output: {'h', 'e', 'l', 'o'} (note: no duplicates)

Practical Examples

Example 1: Student Management System

python

# A simple student management system
students = [
    {
        'id': 1,
        'name': 'John Doe',
        'age': 20,
        'grades': [85, 90, 78, 88]
    },
    {
        'id': 2,
        'name': 'Jane Smith',
        'age': 19,
        'grades': [92, 95, 88, 91]
    }
]

# Calculate average grade for each student
for student in students:
    avg_grade = sum(student['grades']) / len(student['grades'])
    student['average_grade'] = round(avg_grade, 2)
    print(f"Student: {student['name']}, Average Grade: {student['average_grade']}")

# Output:
# Student: John Doe, Average Grade: 85.25
# Student: Jane Smith, Average Grade: 91.5

Example 2: Data Analysis with Different Data Types

python

# A simple data analysis example
# Product sales data
product_sales = {
    'apple': [50, 65, 75, 85, 90],
    'banana': [30, 40, 50, 60, 70],
    'orange': [25, 35, 45, 55, 65]
}

# Calculate total and average sales for each product
product_stats = {}

for product, sales in product_sales.items():
    total_sales = sum(sales)
    avg_sales = total_sales / len(sales)
    
    product_stats[product] = {
        'total_sales': total_sales,
        'average_sales': round(avg_sales, 2),
        'best_day': max(sales),
        'worst_day': min(sales)
    }

# Print the stats
for product, stats in product_stats.items():
    print(f"\nProduct: {product}")
    print(f"  Total Sales: {stats['total_sales']} units")
    print(f"  Average Daily Sales: {stats['average_sales']} units")
    print(f"  Best Day: {stats['best_day']} units")
    print(f"  Worst Day: {stats['worst_day']} units")

# Output:
# Product: apple
#   Total Sales: 365 units
#   Average Daily Sales: 73.0 units
#   Best Day: 90 units
#   Worst Day: 50 units
# ...etc

Checking Data Types

Python provides built-in functions to check data types.

python

# Using type() function
print(type(10))       # Output: <class 'int'>
print(type("hello"))  # Output: <class 'str'>
print(type([1, 2, 3])) # Output: <class 'list'>

# Using isinstance() function
print(isinstance(10, int))     # Output: True
print(isinstance("hello", str)) # Output: True
print(isinstance([1, 2, 3], dict)) # Output: False

Summary

Python data types are the foundation of how we organize and manipulate data in our programs:

• Basic Types: Integers, Floats, Strings, Booleans
• Sequence Types: Lists, Tuples
• Mapping Type: Dictionaries
• Set Types: Sets, Frozen Sets
• None Type: Represents absence of value

Each data type has its own set of operations and methods. Understanding when to use each data type is crucial for effective Python programming.

• Use lists when you need an ordered, mutable collection
• Use tuples when you need an ordered, immutable collection
• Use dictionaries when you need to associate keys with values
• Use sets when you need a collection of unique elements

By mastering Python's data types, you'll be able to write more efficient and effective code.

Exercises

1. Create a list of 5 different data types and use the type() function to confirm their types.
2. Write a program that converts a temperature from Celsius to Fahrenheit using proper numeric data types.
3. Create a dictionary representing a book with attributes like title, author, year, and genres (as a list).
4. Write a function that takes a list of numbers and returns a tuple containing the sum, minimum, and maximum values.
5. Create a program that uses sets to find common elements between two lists.

Additional Resources

• Python Documentation on Data Types
• Python Data Structures Tutorial
• Real Python: Python Data Types
• W3Schools Python Data Types

Remember that mastering Python data types is a fundamental step toward becoming proficient in the language. Practice using different data types in your projects to gain a deeper understanding of when and how to use each one.