Python Fundamentals: Variables and Data Types

Table of Contents

• Variables in Python
• Fundamental Data Types
• Type Conversion and Casting

Variables in Python

In Python, a variable acts as a named storage location that holds a value. Unlike statically-typed languages, Python uses dynamic typing, meaning you don’t explicitly declare a variable’s type; it’s inferred at runtime based on the assigned value. This flexibility simplifies coding but requires careful attention to data types.

Creating Variables:

Variable creation involves assigning a value using the = operator:

name = "Alice"  # String
age = 30       # Integer
height = 5.8   # Float
is_adult = True # Boolean
  

Naming Conventions:

• Start with a letter (a-z, A-Z) or underscore (_).
• Contain letters, numbers (0-9), and underscores.
• Case-sensitive (myVar ≠ myvar).
• Use descriptive names (e.g., user_age instead of x).

Fundamental Data Types

Python offers several built-in data types:

• Integers (int): Whole numbers (e.g., 10, -5, 0).
• Floating-Point Numbers (float): Numbers with decimal points (e.g., 3.14, -2.5, 0.0).
• Strings (str): Sequences of characters enclosed in single (‘ ‘) or double (” “) quotes (e.g., “Hello”, ‘Python’). Strings are immutable (cannot be changed in place).
• Booleans (bool): Represent truth values: True or False.
• NoneType (None): Represents the absence of a value.

Checking Data Types: Use the type() function:

x = 10
print(type(x))  # Output: <class 'int'>
y = "Hello"
print(type(y))  # Output: <class 'str'>
  

Type Conversion and Casting

Converting between data types is often necessary. Python provides built-in functions for this:

str_num = "123"
int_num = int(str_num) # Convert string to integer
print(type(int_num))   # Output: <class 'int'>

float_num = 3.14
int_float = int(float_num) # Convert float to integer (truncates)
print(int_float)          # Output: 3

int_to_str = str(10)      # Convert integer to string
print(type(int_to_str))  # Output: <class 'str'>
  

Note that not all conversions are always possible (e.g., converting “abc” to an integer will raise a ValueError).

This tutorial covered the fundamentals of variables and data types. Further learning involves exploring more advanced data structures like lists, tuples, dictionaries, and sets, which build upon these core concepts.