Numeric type conversion is the process of converting a value from one numeric data type to another.

Python provides built-in functions for converting between numeric types.

The three most commonly used conversion functions are:

• int() – Converts a value to an integer.
• float() – Converts a value to a floating-point number.
• complex() – Converts a value to a complex number.

Type conversion is useful when working with user input, performing calculations, or ensuring that values have the correct data type.

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Syntax #

int(value)
float(value)
complex(value)

Conversion Functions #

Function	Description
int()	Converts a value to an integer.
float()	Converts a value to a floating-point number.
complex()	Converts a value to a complex number.

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Example 1: Convert Integer to Float #

main.py

number = 25

result = float(number)

print(result)
print(type(result))

Output #

25.0
<class 'float'>

Explanation #

• number stores an integer.
• float() converts it into a floating-point number.
• The value becomes 25.0.

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Example 2: Convert Float to Integer #

main.py

number = 15.98

result = int(number)

print(result)
print(type(result))

Output #

15
<class 'int'>

Explanation #

• int() removes the fractional part.
• It does not round the number.
• Therefore, 15.98 becomes 15.

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Example 3: Convert Integer to Complex #

main.py

number = 12

result = complex(number)

print(result)
print(type(result))

Output #

(12+0j)
<class 'complex'>

Explanation #

• complex() converts the integer into a complex number.
• The imaginary part is automatically set to 0j.

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Example 4: Convert Float to Complex #

main.py

number = 8.5

result = complex(number)

print(result)

Output #

(8.5+0j)

Explanation #

• A floating-point value can also be converted into a complex number.
• The imaginary part is 0j.

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Example 5: Convert String to Integer #

main.py

number = "250"

result = int(number)

print(result)
print(type(result))

Output #

250
<class 'int'>

Explanation #

• The original value is a string.
• int() converts the numeric string into an integer.
• The data type changes from str to int.

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Example 6: Convert String to Float #

main.py

number = "45.75"

result = float(number)

print(result)
print(type(result))

Output #

45.75
<class 'float'>

Explanation #

• float() converts the numeric string into a floating-point number.
• The decimal value is preserved.

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Example 7: User Input Conversion #

main.py

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

print(age)
print(type(age))

Sample Input #

21

Output #

21
<class 'int'>

Explanation #

• input() always returns a string.
• int() converts the input into an integer.
• The converted value can be used in calculations.

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Example 8: Arithmetic After Conversion #

main.py

price = "100"

total = int(price) + 50

print(total)

Output #

150

Explanation #

• The string "100" cannot be added directly to an integer.
• int() converts it into a numeric value.
• Arithmetic can then be performed normally.

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Example 9: Convert Boolean Values #

main.py

print(int(True))
print(float(False))

Output #

1
0.0

Explanation #

• True is converted to 1.
• False is converted to 0.
• Boolean values behave like integers during numeric conversion.

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Example 10: Checking Multiple Conversions #

main.py

print(type(int(5.5)))
print(type(float(5)))
print(type(complex(5)))

Output #

<class 'int'>
<class 'float'>
<class 'complex'>

Explanation #

• int(5.5) returns an integer.
• float(5) returns a floating-point number.
• complex(5) returns a complex number.
• Each conversion changes the data type appropriately.

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Common Mistakes #

1. Expecting int() to Round Numbers #

Incorrect

print(int(8.9))

Incorrect Expectation #

9

Actual Output #

8

Reason

int() removes the fractional part instead of rounding the value.

Correct

print(round(8.9))

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2. Converting a Non-Numeric String #

Incorrect

print(int("hello"))

Output #

ValueError: invalid literal for int() with base 10: 'hello'

Reason

Only strings representing valid numbers can be converted to numeric types.

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3. Passing a Complex Number to int() #

Incorrect

print(int(3 + 4j))

Output #

TypeError: can't convert complex to int

Reason

Complex numbers cannot be converted directly to integers.

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4. Expecting Conversion Functions to Modify the Original Variable #

Incorrect

number = "25"

int(number)

print(type(number))

Output #

<class 'str'>

Reason

Conversion functions return a new value.
They do not modify the original variable.

Correct

number = int(number)

print(type(number))

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Best Practices #

• Convert values to the required data type before performing calculations.
• Always validate user input before converting it.
• Remember that int() truncates the fractional part instead of rounding.
• Store the converted value if it will be used later.
• Use the conversion function that matches the required numeric type.

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Key Points to Remember #

• Python provides int(), float(), and complex() for numeric type conversion.
• int() converts values to integers by removing the fractional part.
• float() converts values to floating-point numbers.
• complex() converts values to complex numbers.
• Numeric strings can be converted if they contain valid numeric data.
• Conversion functions return new values and do not modify the original variables.
• Invalid conversions raise exceptions such as ValueError or TypeError.