Python Type Conversion

Type conversion is the process of converting a value from one data type to another. Python provides several built-in functions for converting values between different data types.

For example, a string containing a number can be converted into an integer using int(), while an integer can be converted into a floating-point number using float().

Types of Type Conversion

Python type conversion can be classified into two main types:

1. Implicit Type Conversion

In implicit type conversion, Python automatically converts one compatible data type into another without requiring the programmer to specify the conversion.

This commonly occurs when integer and floating-point values are used together in an arithmetic expression.

a = 10
b = 2.5

result = a + b

print(result)
print(type(result))

12.5
<class 'float'>

Here, a is an integer and b is a float. Python automatically converts the integer to a floating-point value for the calculation.

Another Example of Implicit Conversion

x = 5
y = 2.0

z = x * y

print(z)
print(type(z))

10.0
<class 'float'>

2. Explicit Type Conversion

In explicit type conversion, the programmer manually converts a value from one data type to another by using a conversion function.

Common conversion functions include int(), float(), str(), bool(), list(), tuple() and set().

x = "25"

number = int(x)

print(number)
print(type(number))

25
<class 'int'>

3. Converting to Integer Using int()

The int() function converts a compatible value into an integer.

String to Integer

value = "100"

number = int(value)

print(number)
print(type(number))

100
<class 'int'>

Float to Integer

When a floating-point value is converted to an integer, the fractional part is removed. The value is not rounded to the nearest integer.

value = 25.75

number = int(value)

print(number)

25

Negative Float to Integer

value = -25.75

print(int(value))

-25

The int() conversion truncates the fractional part toward zero.

4. Converting to Float Using float()

The float() function converts a compatible value into a floating-point number.

Integer to Float

number = 25

value = float(number)

print(value)
print(type(value))

25.0
<class 'float'>

String to Float

value = "99.50"

number = float(value)

print(number)
print(type(number))

99.5
<class 'float'>

5. Converting to String Using str()

The str() function converts a value into a string. This is useful when numeric values need to be combined with text.

number = 100

text = str(number)

print(text)
print(type(text))

100
<class 'str'>

Using str() with Text

age = 20

message = "My age is " + str(age)

print(message)

My age is 20

6. Converting to Boolean Using bool()

The bool() function converts a value into either True or False.

print(bool(1))
print(bool(0))
print(bool(10))
print(bool(-5))

True
False
True
True

Boolean Conversion of Strings

A non-empty string is considered true, while an empty string is considered false.

print(bool("Python"))
print(bool("False"))
print(bool(""))

True
True
False

7. Converting List to Tuple

The tuple() function can convert a list into a tuple.

numbers = [10, 20, 30]

result = tuple(numbers)

print(result)
print(type(result))

(10, 20, 30)
<class 'tuple'>

8. Converting Tuple to List

The list() function can convert a tuple into a list.

values = (10, 20, 30)

result = list(values)

print(result)
print(type(result))

[10, 20, 30]
<class 'list'>

9. Converting List to Set

The set() function converts an iterable into a set. Duplicate values are automatically removed.

numbers = [10, 20, 10, 30, 20]

result = set(numbers)

print(result)

{10, 20, 30}

A set is unordered, so the displayed order of its elements should not be relied upon.

10. Converting String to List

Using list() on a string creates a list containing its individual characters.

text = "Python"

result = list(text)

print(result)

['P', 'y', 't', 'h', 'o', 'n']

11. Converting String to Tuple

text = "ABC"

result = tuple(text)

print(result)

('A', 'B', 'C')

12. Converting String to Set

text = "hello"

result = set(text)

print(result)

A set stores only unique elements and does not guarantee a particular display order.

13. Type Conversion of User Input

The input() function returns the entered value as a string. Therefore, conversion is normally required when numerical calculations are performed.

age = input("Enter your age: ")

print(type(age))

Enter your age: 20
<class 'str'>

To receive the age as an integer, use int().

age = int(input("Enter your age: "))

print(age)
print(type(age))

Enter your age: 20
20
<class 'int'>

14. Multiple Input with Type Conversion

The map() function can be used with a conversion function to convert multiple input values.

a, b, c = map(int, input("Enter three numbers: ").split())

print("Sum =", a + b + c)

Enter three numbers: 10 20 30
Sum = 60

15. Type Conversion in Arithmetic Operations

Type conversion is frequently used when a program receives numeric values as strings.

a = "10"
b = "20"

result = int(a) + int(b)

print("Sum =", result)

Sum = 30

Without conversion, the + operator would concatenate the two strings instead of performing numeric addition.

a = "10"
b = "20"

print(a + b)

1020

16. Invalid Type Conversion

A conversion may fail if the value is not compatible with the requested data type.

value = "Hello"

number = int(value)

print(number)

The above program raises a ValueError because "Hello" cannot be converted into an integer.

17. Checking the Type After Conversion

The type() function can be used to check the data type before and after conversion.

value = "50"

number = int(value)

print("Before:", type(value))
print("After:", type(number))

Before: <class 'str'>
After: <class 'int'>

Common Type Conversion Functions

Implicit vs Explicit Type Conversion

Important Points

• Type conversion changes a value from one data type to another.
• Implicit conversion is performed automatically by Python.
• Explicit conversion is performed by the programmer.
• int() converts compatible values to integers.
• float() converts compatible values to floating-point numbers.
• str() converts a value into a string.
• bool() converts a value into True or False.
• list(), tuple() and set() can convert compatible iterables.
• input() returns user input as a string.
• Invalid conversions can raise exceptions such as ValueError.
• The type() function can be used to verify the resulting data type.