What is Type Casting?

Type casting is the process of converting one possible type of value into another type of value.

You already met this idea when keyboard input returned a string. Before multiplication, that string had to become a number.

What you'll learn

• Convert one value type into another
• Understand why input() and APIs usually return text
• Use the five fundamental casting functions
• Recognize which conversions succeed and which fail

Why do we convert types?

Python is dynamically typed, but every value has one type at a time.

Situation	What happens
Keyboard input	"3.5" → 3.5 using float()
Whole-number math	12.99 → 12 using int()
Conditions	100 → True using bool()
Display text	100 → "100" using str()

Five fundamental casting functions

Function	Converts into
int()	Integer numbers
float()	Decimal numbers
bool()	True or False
complex()	Complex numbers
str()	Text / strings

General syntax

new_value = int(value)
new_value = float(value)
new_value = bool(value)
new_value = complex(value)
new_value = str(value)

The argument must be a possible source type. Later lessons show exactly which combinations work.

Interactive playground

Change the input and instantly see which conversions succeed.

Possible vs not possible

Not every conversion is allowed.

Result	Example
Possible	int(12.34) → 12
Possible	float("12.34") → 12.34
TypeError	int(2+3j)
ValueError	int("12.34")

Remember the difference

• TypeError: The value’s type cannot be converted.
• ValueError: The type is valid, but the content is invalid.

This module focuses on those five converters. Collection conversions (list(), tuple(), set(), dict()) come later.

Real Python example

text = "12"

number = int(text)

print(number)
print(type(number))

12
<class 'int'>

The original string is not modified. Python creates a new integer object.

Practice exercises

1. Print type("10") and type(int("10")).
2. Predict whether float("10") works, then run it.
3. Test int("10.5") and observe the ValueError.

Quick knowledge check

1. What is type casting?
   Converting one possible type of value into another type of value.

2. Name the five fundamental converters.
   int(), float(), bool(), complex(), str()

3. Does every conversion succeed?
   No. Invalid conversions raise either TypeError or ValueError.

Summary

• Type casting converts one value type into another.
• Python has five fundamental casting functions.
• Success depends on the source type and, for strings, the text content.
• The next lesson explores int() in depth with every valid and invalid conversion.