Python Casting (Type conversion)

Learn type conversion and typecasting. Convert variable declared in specific data type to different data types.

In Python, we can convert one type of variable to another type. This conversion is called type casting or type conversion.

In casting, we convert variables declared in specific data types to the different data types.

Python performs the following two types of casting.

Implicit casting: The Python interpreter automatically performs an implicit Type conversion, which avoids loss of data.
Explicit casting: The explicit type conversion is performed by the user using built-in functions.

To perform a type casting, we are going to use the following built-in functions

int(): convert any type variable to the integer type.
float(): convert any type variable to the float type.
complex(): convert any type variable to the complex type.
bool(): convert any type variable to the bool type.
str(): convert any type variable to the string type.

In type casting, data loss may occur because we enforce the object to a specific data type.

Int type conversion

In int type conversion, we use the int() function to convert variables of other types to int type. Variable can be of any type such as float, string, bool.

While performing int type conversion, we need to remember the following points.

When converting string type to int type, a string must contain integral value only and should be base-10.
We can convert any type to int type, but we cannot perform complex to int type.

Example: Casting float value to an integer

pi = 3.14  # float number
print(type(pi))
# Output class 'float'

# converting float integer
num = int(pi)

print("Integer number:", num)
# Output  3

print(type(num))
# Output class 'int'

<class 'float'>
Integer number: 3
<class 'int'>

Example: Casting Boolean value to an integer

flag_true = True
flag_false = False
print(type(flag_true))
# Output class 'bool'

# converting boolean to integer
num1 = int(flag_true)
num2 = int(flag_false)

print("Integer number 1:", num1)  
# Output 1
print(type(num1))  
# Output class 'int'

print("Integer number 2:", num2)
# 0
print(type(num2))
# class 'int'

<class 'bool'>
Integer number 1: 1

<class 'int'>
Integer number 2: 0
<class 'int'>

Example: Casting a string to an integer

string_num = "225"
print(type(string_num))
# Output class 'str'

# converting str to integer
num1 = int(string_num)

print("Integer number 1:", num1)
# Output 225
print(type(num1))
# Output class 'int'

<class 'str'>
Integer number 1: 225
<class 'int'>

When converting string type to int type, a string must contain integral value only and should be base-10. If you try to convert

string_num = 'Score is 25'
print(type(string_num))
# Output class 'str'

# ValueError: invalid literal for int() with base 10: 'Score is 25'
num = int(string_num)
print(num)

Float type conversion

In float type conversion we use a built-in function float() . This function converts variables of other types to float types.

Example: Casting integer to float

num = 725
print(type(num))
# Output class 'int'

# converting float to integer
num1 = float(num)

print("Float number:", num1)
# Output 725.0
print(type(num1))
# Output class 'float'

<class 'int'>
Float number: 725.0
<class 'float'>

Example: Casting Boolean to float

flag_true = True
flag_false = False
print(type(flag_true)) 
# Output class 'bool'

# converting boolean to float
num1 = float(flag_true)
num2 = float(flag_false)

print("Float number 1:", num1)
# Output 1.0
print(type(num1))
# class 'float'

print("Float number 2:", num2)
# Output 0.0
print(type(num2))
# class 'float'

Example: Casting string to float

string_num = "725.535"
print(type(string_num))
# Output class 'str'

# converting str to float
num1 = float(string_num)

print("Float number:", num1)
# Output 725.535
print(type(num1))
# class 'float'

While performing float type conversion, we need to remember some points.

We can convert any type to float type, but we cannot cast complex to float type.
While converting string type to float type, a string must contain an integer/decimal value of base-10.

Complex type conversion

In complex type conversion, we use the built-in function complex() to convert values from other types to the complex type. Value can be any type including of int, float, bool, str.

The complex function has the following two forms for conversion.

complex(x): To convert a value x into a complex type. In this form, the real value is x, and the imaginary value is 0.
complex(x, y): To convert the value x and y into a complex type. In this form, the real value is x, and the imaginary is y.

Example: Casting integer type to complex type

r_num = 135
print(type(r_num)) # class 'int'

# converting int to complex(x)
c_num = complex(r_num)

print("Complex number:", c_num)
# Output (135+0j)
print(type(c_num))
# class 'complex'

# converting int to complex(x, y)
r_num, i_num2 = 135, 235
c_num = complex(r_num, i_num2)

print("Complex number:", c_num)
# Output (135+235j)
print(type(c_num))  # class 'complex'

class 'int'>
Complex number: (135+0j)
<class 'complex'>
Complex number: (135+235j)
<class 'complex'>

Example: Casting float type to complex type

r_num = 53.250
print(type(r_num))  # class 'float'

# converting float to complex(x)
c_num = complex(r_num)

print("Complex number:", c_num)
# Output (53.25+0j)
print(type(c_num))  
# class 'complex'

# converting float to complex(x, y)
r_num, i_num2 = 53.250, 350.750
c_num = complex(r_num, i_num2)

print("Complex number:", c_num)
# Output (53.25+350.75j)
print(type(c_num))
# class 'complex'

<class 'float'>
Complex number: (53.25+0j)
<class 'complex'>
Complex number: (53.25+350.75j)
<class 'complex'>

Example: Casting Boolean type to complex type

boolean_true = True
print(type(boolean_true))  # class 'bool'

# converting boolean to complex(x)
c_num = complex(boolean_true)

print("Complex number:", c_num)  
# Output (1+0j)
print(type(c_num))
# class 'complex'

# converting boolean to complex(x, y)
r_bool, i_bool = False, True
c_num = complex(r_bool, i_bool)

print("Complex number:", c_num)
# Output 1j
print(type(c_num))
# class 'complex'

<class 'bool'>
Complex number: (1+0j)
<class 'complex'>
Complex number: 1j
<class 'complex'>

Bool type conversion

We use the built-in function bool() to convert values of other types to bool types. This function returns two values, either True or False.

We can convert any type of values to bool type, and the output for all values will be True, Except 0, which is False.
If you convert an empty string to a boolean it will be converted to boolean False.

The bool True is 1 and False is 0. Every non-zero value is treated as True.

Example: Casting integer to Boolean type

num1 = 10
num2 = 0
print(type(num1))  # class 'int'

# Convert into to bool
b1 = bool(num1)
b2 = bool(num2)

print(b1)
# Output True
print(b2)
# Output False

print(type(b1))
# class 'bool'

Example: Casting float to Boolean type

f_num1 = 25.35
f_num2 = 0.0
print(type(f_num1))  # class 'float'

# Convert float into to bool
b1 = bool(f_num1)
b2 = bool(f_num2)

print(b1)
# Output True

print(b2)
# Output False

print(type(b1))
# Output class 'bool'

Example: Casting string to Boolean type

s1 = "False"
s2 = "True"
s3 = "812"
s4 = ""
print(type(s1))  # class 'str'

# Convert string into to bool
b1 = bool(s1)
b2 = bool(s2)
b3 = bool(s3)
b4 = bool(s4)

print(b1)  # True
print(b2)  # True
print(b3)  # True
print(b4)  # False
print(type(b1))  # class 'bool'

Example: Casting complex type to Boolean type

c1 = 33 + 9j
c2 = 0 + 0j
print(type(c1))  # class 'complex'

# Convert complex value into to bool
b1 = bool(c1)
b2 = bool(c2)

print(b1)  # True
print(b2)  # False
print(type(b1))  # class 'bool'

String type conversion

In str type conversion, we use the built-in function str() to convert converts variables of other types to a string type. This function returns the string type of object (value).

Example: Casting int to str type

num = 15
print(type(num))  # class 'int'

# converting int to str type
s1 = str(num)
print(s1)
# Output '15'
print(type(s1))
# Output class 'str'

Example: Casting float type to str type

num = 75.35
print(type(num))  # class 'float'

# converting float to str type
s1 = str(num)
print(s1)
# Output '75.35'
print(type(s1))
# Output class 'str'

Example: Casting complex type to str type

complex_num = 15 + 5j
print(type(complex_num))  # class 'complex'

# converting complex to str type
s1 = str(complex_num)
print(s1)
# Output '(15+5j)'

print(type(s1))
# class 'str'

Example: Casting bool type to str type

b1 = True
b2 = False
print(type(b1))  # class 'bool'

# converting bool to str type
s1 = str(b1)
s2 = str(b2)
print(s1)
# Output 'True'
print(s2)
# Output 'False'
print(type(s1))  # class 'str'