Type Casting in Python

Type Casting is the method to convert the Python variable datatype into a certain data type in order to perform the required operation by users. We will see various techniques for typecasting. There can be two types of Type Casting in Python:

• Implicit Type Conversion
• Explicit Type Conversion

Example: The following code converts a numeric string into an integer so it can be used in arithmetic operations.

age = "21"
age = int(age)
print(age + 5)
print(type(age))

26
<class 'int'>

Implicit Type Conversion

Implicit type conversion is the automatic changing of a data value from one type to another by the compiler or runtime environment without any manual intervention from the programmer

# Python automatically converts 'a' to int 
a = 7
print(type(a)) 

# Python automatically converts 'b' to float 
b = 3.0
print(type(b)) 

# Python automatically converts 'c' to float as it is a float addition 
c = a + b 
print(c) 
print(type(c))

# Python automatically converts 'd' to float as it is a float multiplication
d = a * b
print(d)
print(type(d))

<class 'int'>
<class 'float'>
10.0
<class 'float'>
21.0
<class 'float'>

Explanation:

• a is an integer and b is a floating-point number.
• During a + b, Python automatically converts a to float, so c becomes 10.0.
• During a * b, Python again converts a to float, so d becomes 21.0.
• Since the operations involve both int and float, the results are returned as float.
• This automatic conversion is known as implicit type conversion.

Explicit Type Conversion

Explicit type conversion is when the programmer manually changes a value’s data type using built-in type casting functions, usually when automatic conversion is not possible or a specific type is needed.

Examples of Type Casting

Commonly used type casting functions in Python are:

• Int() function take float or string as an argument and returns int type object.
• float() function take int or string as an argument and return float type object.
• str() function takes float or int as an argument and returns string type object.

Convert Int to Float

Converting Int to Float in with the float() function.

a = 5
n = float(a)

print(n)
print(type(n))

5.0
<class 'float'>

Python Convert Float to Int 

Converting Float to int datatype in Python with int() function.

a = 5.9
n = int(a)

print(n)
print(type(n))

5
<class 'int'>

Python Convert int to String 

Converting int to String datatype in Python with str() function.

a = 5

# typecast to str
n = str(a)

print(n)
print(type(n))

5
<class 'str'>

Python Convert String to float

Casting string data type into float data type with float() function.

a = "5.9"
n = float(a)

print(n)
print(type(n))

5.9
<class 'float'>

Python Convert string to int

Converting string to int datatype in Python with int() function. If the given string is not number, then it will throw an error.

a = "5"
b = 't'
n = int(a)

print(n)
print(type(n))

print(int(b))
print(type(b))

Output

5
<class 'int'>
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
/tmp/ipython-input-1957009883.py in <cell line: 0>()
9 print(type(n))
10
---> 11 print(int(b))
12 print(type(b))
ValueError: invalid literal for int() with base 10: 't'

The string "5" is successfully converted into an integer 5. Since 't' is not a number, Python cannot convert it into an integer.

Adding String and Integer Without Conversion

If we try to directly add an integer and a string, Python will throw an error because they are different data types.

a = 5
b = 't'

n = a+b

print(n)
print(type(n))

Output

TypeError: unsupported operand type(s) for +: 'int' and 'str'

We should first convert the string into an integer and then add:

a = 5
b = '7'

# explicit conversion of string to int
n = a + int(b)
print(n)        
print(type(n))