Casting and Data Type Conversion in Python

Python

Learn Python Programming: A Beginner’s Guide to Coding, Automation, and Data Science

What is Type Casting? 

Imagine you have a magical potion that can transform objects into different forms. In Python, type casting (or type conversion) allows you to change a value’s data type, like turning a pumpkin into a carriage (or an integer into a float). 

Python provides built-in functions to convert one data type to another:

• int() → Converts to an integer (whole number)
• float() → Converts to a floating-point (decimal number)
• str() → Converts to a string (text)
• bool() → Converts to a boolean (True or False)

Converting to an Integer (int) 

If you have a string or a float and need an integer, you can use int().

Example:

num_str = "42"
num_int = int(num_str)  # Converts string "42" to integer 42
print(num_int)  # Output: 42

Be careful when converting from float to int:

num_float = 3.99
num_int = int(num_float)
print(num_int)  # Output: 3 (Python TRUNCATES, no rounding!)

Important: If you try to convert a non-numeric string, Python will complain:

num = int("Hello")  #  ERROR: ValueError

Converting to a Float (float) 

Need decimals? Use float() to convert an integer or a string.

Example:

num_int = 10
num_float = float(num_int)  # Converts 10 to 10.0
print(num_float)  # Output: 10.0

Works with strings too:

num_str = "3.14"
num_float = float(num_str)
print(num_float)  # Output: 3.14

Trying to convert a string that isn’t a number?

num = float("Hello")  #  ERROR: ValueError

Converting to a String (str) 

Need to turn numbers into text? str() is your friend.

Example:

age = 25
age_str = str(age)
print("I am " + age_str + " years old.")  # Output: I am 25 years old.

This is useful when printing or combining text with numbers.

price = 9.99
print("The price is $" + str(price))  # Output: The price is $9.99

Converting to a Boolean (bool) 

Python considers some values as False and others as True:

False values:

• 0
• "" (empty string)
• None
• False

Everything else is True:

print(bool(0))      # Output: False
print(bool(1))      # Output: True
print(bool(""))    # Output: False
print(bool("Hello")) # Output: True

Even non-empty lists and dictionaries are True:

print(bool([]))     # Output: False (empty list)
print(bool([1, 2])) # Output: True (non-empty list)

Summary 

Function	Converts To
int(x)	Integer (removes decimals if float)
float(x)	Float (adds .0 if integer)
str(x)	String
bool(x)	Boolean (False for 0, "", None; True otherwise)

Now you know how to cast and convert data types in Python like a pro!