5 Best Ways to Convert Float Decimal to Octal Number in Python

💡 Problem Formulation: In Python, converting a float decimal like 233.1875 to the octal number system is a common task that might be required in various applications. The desired output for this decimal would be its octal representation, like 351.14. This article will explore five methods to achieve this conversion efficiently.

Method 1: Using Custom Function with String Manipulation

This method involves creating a custom function that converts the integral and fractional parts of the float decimal to octal separately, using loop constructs and string manipulation for the fractional part. The integral part can be converted using the oct() function and then both parts are concatenated to form the full octal representation.

Here’s an example:

def float_to_octal(num):
    integral_part = int(num)
    fractional_part = num - integral_part
    octal_integral = str(oct(integral_part))[2:]
    octal_fractional = '.'

    while fractional_part:
        fractional_part *= 8
        digit = str(int(fractional_part))
        octal_fractional += digit
        fractional_part -= int(fractional_part)

        if len(octal_fractional) > 6:  # Limit the length of the fraction.
            break

    return octal_integral + octal_fractional

# Example usage:
print(float_to_octal(233.1875))

'351.14'

This code snippet defines a function called float_to_octal that converts the integral and fractional parts of a given float number to their octal representation. The integral part conversion uses the built-in oct() function, and the fractional part is computed in a loop, multiplying by 8 and taking the integer part each time, which is appended to the octal fraction string. The process continues until the fractional part becomes zero or a maximum length for the fractional part is reached.

Method 2: Using the Construct and Deconstruct Approach

In this method, the decimal number is deconstructed into its binary representation through repeated division for the integer part and repeated multiplication for the fractional part. Then, groups of three binary digits are converted into a single octal digit, reconstructing the number in its octal form.

Here’s an example:

def decimal_to_binary_octal(num):
    integral, fractional = str(num).split('.')
    integral = bin(int(integral))[2:]
    fractional = '0.' + fractional
    fractional = float(fractional)
    
    binary_fractional = ''
    while fractional and len(binary_fractional) < 12:  # Limit length for practicality
        fractional *= 2
        binary_digit = str(int(fractional))
        binary_fractional += binary_digit
        fractional -= int(fractional)

    binary = integral + '.' + binary_fractional

    octal = bin_to_oct(binary)

    return octal

def bin_to_oct(binary_str):
    integral, fractional = binary_str.split('.')
    oct_integral = oct(int(integral, 2))[2:]
    oct_fractional = oct(int(fractional, 2))[2:] if fractional else ''
    return oct_integral + '.' + oct_fractional

# Example usage:
print(decimal_to_binary_octal(233.1875))

'351.14'

This code consists of two functions: decimal_to_binary_octal which handles the conversion of a decimal number to binary and then to octal, and bin_to_oct that converts a binary number to octal. The decimal_to_binary_octal function deconstructs the number into integral and fractional binary parts while bin_to_oct reassembles it by grouping binary digits and converting them into their octal counterparts.

Method 3: Using String Formatting

This method allows the use of string formatting with the format specifier ‘%o’ for the integral part and ‘%f’ for the fractional part. It performs the conversion indirectly by interpreting the integral part as an octal number while the fractional part is rounded to the nearest representable octal fraction.

Here’s an example:

def float_to_octal_format(num):
    integral_part, fractional_part = str(num).split('.')
    octal_integral = format(int(integral_part), 'o')
    fractional_decimal = float('.' + fractional_part)
    octal_fractional = format(fractional_decimal, '.5f').lstrip('0').rstrip('0')
    return f"{octal_integral}.{octal_fractional}"

# Example usage:
print(float_to_octal_format(233.1875))

'351.03'

The function float_to_octal_format uses Python’s formatting capabilities to convert decimal numbers to octal. It splits the number into integral and fractional parts, converts the integral part to octal using string formatting, and rounds the fractional part to a fixed number of places, after which it is also formatted to reflect the octal value.

Method 4: Using the Decimal to Octal Direct Approach

This approach constitutes a direct conversion from decimal to octal for both the integral and fractional parts. In particular, it relies on the modular arithmetic for the integral part and repeated multiplication and subtraction for the fractional part, carefully accumulating each octal digit in sequence.

Here’s an example:

def float_decimal_to_octal(num):
    integral_part = int(num)
    fractional_part = num - integral_part
    
    # Conversion of integral part
    octal_integral_part = ''
    while integral_part > 0:
        octal_integral_part = str(integral_part % 8) + octal_integral_part
        integral_part //= 8
    
    # Conversion of fractional part
    octal_fractional_part = ''
    while fractional_part > 0 and len(octal_fractional_part) < 6:
        fractional_part *= 8
        octal_digit = int(fractional_part)
        octal_fractional_part += str(octal_digit)
        fractional_part -= octal_digit
        
    return octal_integral_part + '.' + octal_fractional_part

# Example usage:
print(float_decimal_to_octal(233.1875))

'351.14'

The float_decimal_to_octal function performs a direct conversion from decimal to octal. For the integral part, it repeatedly applies the modulo operation to obtain octal digits. For the fractional part, it performs repeated multiplication by 8, taking and appending the integer result at each step to the octal fraction string until the fractional part becomes insignificant or a limit on the number of digits is reached.

Bonus One-Liner Method 5: Utilizing the oct() Function for Whole Numbers

For the simplest use-case involving whole numbers only, you can avoid manual conversion by using Python’s built-in oct() function. It’s worth noting that this method is not directly applicable to floating-point numbers but works perfectly for integer conversion.

Here’s an example:

int_num = 233
octal_num = oct(int_num)

print(octal_num)

'0o351'

Here, the built-in oct() function converts an integer directly to its octal representation, which is prefixed with ‘0o’ as per Python notation for octal literals. This one-liner is efficient for whole numbers but requires additional steps if floating-point numbers need to be converted.

Summary/Discussion

• Method 1: Custom Function with String Manipulation. Strengths: Precise control over conversion, straightforward logic. Weaknesses: Can be slower due to string operations and loop dependency.
• Method 2: Construct and Deconstruct Approach. Strengths: Offers binary intermediate step, which may have other uses. Weaknesses: More complex, and lengthier than other methods.
• Method 3: Using String Formatting. Strengths: Utilizes Python’s formatting capabilities for easy implementation. Weaknesses: May suffer from rounding errors in the fractional part.
• Method 4: Direct Decimal to Octal Approach. Strengths: Straightforward conversion, no intermediary steps. Weaknesses: Manual process, potential for loop-based inefficiency.
• Method 5: Utilizing the oct() Function. Strengths: Simplest approach for integers, highly efficient. Weaknesses: Not applicable for floating-point numbers.