Type Casting in Python

In Python programming, type conversion (also known as type casting) is the process of converting one data type into another. Python supports multiple ways of converting types, making it simple yet powerful for managing data.

1. What is Type Conversion?

Type conversion in Python refers to changing data from one type to another explicitly or implicitly. For example:

• Converting a string "10" into an integer 10.
• Converting an integer 3 into a float 3.0.

This technique is especially useful when working with data from external sources (like user input, files, or web APIs) where data type mismatches may occur.

2. Types of Type Conversion

Python offers two kinds of type conversions:

a) Implicit Type Conversion

Implicit type conversion (automatic type conversion) occurs when Python converts one data type to another automatically during operations.

x = 10      # integer
y = 2.5     # float

result = x + y  # integer is implicitly converted to float
print(result)   # 12.5
print(type(result))  # <class 'float'>

Python automatically converts the integer (10) to a float (10.0) to avoid data loss.

b) Explicit Type Conversion

Explicit type conversion involves manually converting a data type using built-in functions.

num_str = "123"       # String
num_int = int(num_str)  # Explicitly converting to integer
print(num_int)        # 123
print(type(num_int))  # <class 'int'>

3. Common Type Conversion Functions

Python provides built-in functions for explicit type conversions:

4. Examples of Type Conversions

Here are practical examples demonstrating type conversions:

a) String to Integer

age_str = "25"
age_int = int(age_str)
print(age_int, type(age_int))

b) Integer to Float

x = 5
x_float = float(x)
print(x_float, type(x_float))

c) Float to Integer (Truncation)

pi = 3.14159
pi_int = int(pi)  # Removes decimal part
print(pi_int)  # 3

d) String to List

name = "Alice"
name_list = list(name)
print(name_list)  # ['A', 'l', 'i', 'c', 'e']

e) List to Set

numbers = [1, 2, 2, 3, 3]
unique_numbers = set(numbers)
print(unique_numbers)  # {1, 2, 3}

f) Tuple to Dictionary

pairs = [("a", 1), ("b", 2)]
dict_pairs = dict(pairs)
print(dict_pairs)  # {'a': 1, 'b': 2}

g) Boolean Conversion

print(bool(0))      # False
print(bool(5))      # True
print(bool(""))     # False
print(bool("Python")) # True

5. Errors in Type Conversions

Type conversion can cause errors when incompatible conversions are attempted:

invalid_int = int("hello")  # Raises ValueError

Common Errors:

• ValueError: Occurs when data cannot be converted logically.
• TypeError: Occurs when a non-iterable is used where an iterable is expected (e.g., converting an integer directly into a list).

Preventing errors:

• Always validate data before converting.
• Use try-except blocks for error handling.

try:
    number = int("ten")
except ValueError:
    print("Conversion failed. Invalid integer.")