Day-2 - Type Casting in Python

In Python, type casting (also known as type conversion) is the process of converting a value from one data type to another.

This is especially useful when working with user input, mathematical operations, or when you need to ensure data is in the right format.

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Why Do We Need Type Casting? 🤔

Consider this example:

age = input("Enter your age: ")
print(age + 5)   # ❌ Error

Here, input() always returns a string, even if you enter a number. Trying to add a string and an integer will throw an error.

✅ Solution: Convert the string into an integer using type casting:

age = int(input("Enter your age: "))
print(age + 5)   # Works fine

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Types of Type Casting in Python

Python supports two types of conversions:

1. Explicit Type Casting (Manual Conversion)

You manually convert values using built-in functions like int(), float(), str(), bool().

👉 Example:

# String to Integer
print(int("100"))       # 100

# Float to Integer (decimal part removed)
print(int(9.99))        # 9

# Integer to String
print(str(123))         # "123"

# Number to Boolean
print(bool(0))          # False
print(bool(5))          # True

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2. Implicit Type Casting (Automatic Conversion)

Sometimes, Python automatically converts data types during operations.

👉 Example:

x = 10       # Integer
y = 2.5      # Float

result = x + y
print(result)        # 12.5
print(type(result))  # <class 'float'>

Here, Python automatically promotes the integer (10) into a float so that both operands are of the same type.

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Common Conversion Functions

1. int() → Converts values into integers (removes decimals, errors on invalid strings).

2. float() → Converts values into floating-point numbers.

3. str() → Converts numbers, booleans, or other objects into strings.

4. bool() → Converts values into True or False.

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Edge Cases ⚡

1. Converting an invalid string to a number → ❌ Error

    print(int("abc"))  # ValueError
   

2. Boolean conversion rules:

    print(bool(""))     # False  (empty string)
    print(bool("Hi"))   # True   (non-empty string)
    print(bool(0))      # False
    print(bool(42))     # True
   

3. Float to int always truncates, not rounds:

    print(int(9.99))   # 9
    print(int(-3.9))   # -3
   

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Quick Recap 🚀

• Type Casting = Converting one data type into another.

• Explicit Casting → Done using functions (int(), float(), str(), bool()).

• Implicit Casting → Done automatically by Python during operations.

• Be mindful of edge cases (invalid strings, float truncation, boolean rules).

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✨ With type casting, Python gives you complete control over how data behaves in your program — making it flexible, safe, and beginner-friendly!