Tag: type conversion of cpp

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Python Type Conversion and Type Casting

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In this article, you will learn about the Type conversion and uses of type conversion.

Before learning Type Conversion in Python, you should have knowledge about Python Data Types.

Type Conversion

The process of converting the value of one data type (integer, string, float, etc.) to another data type is called type conversion. Python has two types of type conversion.

  1. Implicit Type Conversion
  2. Explicit Type Conversion

Implicit Type Conversion

In Implicit type conversion, Python automatically converts one data type to another data type. This process doesn’t need any user involvement.

Let’s see an example where Python promotes the conversion of the lower data type (integer) to the higher data type (float) to avoid data loss.

Example 1: Converting integer to float

num_int = 123
num_flo = 1.23

num_new = num_int + num_flo

print("datatype of num_int:",type(num_int))
print("datatype of num_flo:",type(num_flo))

print("Value of num_new:",num_new)
print("datatype of num_new:",type(num_new))

When we run the above program, the output will be:

datatype of num_int: <class 'int'>
datatype of num_flo: <class 'float'>

Value of num_new: 124.23
datatype of num_new: <class 'float'>

In the above program,

  • We add two variables num_int and num_flo, storing the value in num_new.
  • We will look at the data type of all three objects respectively.
  • In the output, we can see the data type of num_int is an integer while the data type of num_flo is a float.
  • Also, we can see the num_new has a float data type because Python always converts smaller data types to larger data types to avoid the loss of data.

Now, let’s try adding a string and an integer, and see how Python deals with it.

Example 2: Addition of string(higher) data type and integer(lower) datatype

num_int = 123
num_str = "456"

print("Data type of num_int:",type(num_int))
print("Data type of num_str:",type(num_str))

print(num_int+num_str)

When we run the above program, the output will be:

Data type of num_int: <class 'int'> 
Data type of num_str: <class 'str'> 

Traceback (most recent call last): 
  File "python", line 7, in <module> 
TypeError: unsupported operand type(s) for +: 'int' and 'str'

In the above program,

  • We add two variables num_int and num_str.
  • As we can see from the output, we got TypeError. Python is not able to use Implicit Conversion in such conditions.
  • However, Python has a solution for these types of situations which is known as Explicit Conversion.

Explicit Type Conversion

In Explicit Type Conversion, users convert the data type of an object to required data type. We use the predefined functions like int(), float(), str(), etc to perform explicit type conversion.

This type of conversion is also called typecasting because the user casts (changes) the data type of the objects.

Syntax :

<required_datatype>(expression)

Typecasting can be done by assigning the required data type function to the expression.

Example 3: Addition of string and integer using explicit conversion

num_int = 123
num_str = "456"

print("Data type of num_int:",type(num_int))
print("Data type of num_str before Type Casting:",type(num_str))

num_str = int(num_str)
print("Data type of num_str after Type Casting:",type(num_str))

num_sum = num_int + num_str

print("Sum of num_int and num_str:",num_sum)
print("Data type of the sum:",type(num_sum))

When we run the above program, the output will be:

Data type of num_int: <class 'int'>
Data type of num_str before Type Casting: <class 'str'>

Data type of num_str after Type Casting: <class 'int'>

Sum of num_int and num_str: 579
Data type of the sum: <class 'int'>

In the above program,

  • We add num_str and num_int variable.
  • We converted num_str from string(higher) to integer(lower) type using int() function to perform the addition.
  • After converting num_str to an integer value, Python is able to add these two variables.
  • We got the num_sum value and data type to be an integer.
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C++, programming languages

C++ Type Conversion

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In this tutorial, we will learn about the basics of C++ type conversion with the help of examples.

C++ allows us to convert data of one type to that of another. This is known as type conversion.

There are two types of type conversion in C++.

  1. Implicit Conversion
  2. Explicit Conversion (also known as Type Casting)

Implicit Type Conversion

The type conversion that is done automatically done by the compiler is known as implicit type conversion. This type of conversion is also known as automatic conversion.

Let us look at two examples of implicit type conversion.

Example 1: Conversion From int to double

// Working of implicit type-conversion

#include <iostream>
using namespace std;

int main() {
   // assigning an int value to num_int
   int num_int = 9;

   // declaring a double type variable
   double num_double;
 
   // implicit conversion
   // assigning int value to a double variable
   num_double = num_int;

   cout << "num_int = " << num_int << endl;
   cout << "num_double = " << num_double << endl;

   return 0;
}

Run Code

Output

num_int = 9
num_double = 9

In the program, we have assigned an int data to a double variable.

num_double = num_int;

Here, the int value is automatically converted to double by the compiler before it is assigned to the num_double variable. This is an example of implicit type conversion.

Example 2: Automatic Conversion from double to int

//Working of Implicit type-conversion

#include <iostream>
using namespace std;

int main() {

   int num_int;
   double num_double = 9.99;

   // implicit conversion
   // assigning a double value to an int variable
   num_int = num_double;

   cout << "num_int = " << num_int << endl;
   cout << "num_double = " << num_double << endl;

   return 0;
}

Run Code

Output

num_int = 9
num_double = 9.99

In the program, we have assigned a double data to an int variable.

num_double = num_int;

Here, the double value is automatically converted to int by the compiler before it is assigned to the num_int variable. This is also an example of implicit type conversion.

Note: Since int cannot have a decimal part, the digits after the decimal point is truncated in the above example.

Data Loss During Conversion (Narrowing Conversion)

As we have seen from the above example, conversion from one data type to another is prone to data loss. This happens when data of a larger type is converted to data of a smaller type.

Data loss in C++ if a larger type of data is converted to a smaller type.
Possible Data Loss During Type Conversion

C++ Explicit Conversion

When the user manually changes data from one type to another, this is known as explicit conversion. This type of conversion is also known as type casting.

There are three major ways in which we can use explicit conversion in C++. They are:

  1. C-style type casting (also known as cast notation)
  2. Function notation (also known as old C++ style type casting)
  3. Type conversion operators

C-style Type Casting

As the name suggests, this type of casting is favored by the C programming language. It is also known as cast notation.

The syntax for this style is:

(data_type)expression;

For example,

// initializing int variable
int num_int = 26;

// declaring double variable
double num_double;

// converting from int to double
num_double = (double)num_int;

Function-style Casting

We can also use the function like notation to cast data from one type to another.

The syntax for this style is:

data_type(expression);

For example,

// initializing int variable
int num_int = 26;

// declaring double variable
double num_double;

// converting from int to double
num_double = double(num_int);

Example 3: Type Casting

#include <iostream>

using namespace std;

int main() {
    // initializing a double variable
    double num_double = 3.56;
    cout << "num_double = " << num_double << endl;

    // C-style conversion from double to int
    int num_int1 = (int)num_double;
    cout << "num_int1   = " << num_int1 << endl;

    // function-style conversion from double to int
    int num_int2 = int(num_double);
    cout << "num_int2   = " << num_int2 << endl;

    return 0;
}

Run Code

Output

num_double = 3.56
num_int1   = 3
num_int2   = 3

We used both the C style type conversion and the function-style casting for type conversion and displayed the results. Since they perform the same task, both give us the same output.

Type Conversion Operators

Besides these two type castings, C++ also has four operators for type conversion. They are known as type conversion operators. They are:

  • static_cast
  • dynamic_cast
  • const_cast
  • reinterpret_cast

We will learn about these casts in later tutorials.

Recommended Tutorials:

  • C++ string to int and Vice-versa
  • C++ string to float, double and Vice-versa
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