Python Programs | IT Developer
IT Developer

Python Programs

Share with a Friend
Previous
HOME
Next

Show precision differences between float and Decimal - Python Program

The following program demonstrates the precision differences between float and Decimal types in Python, particularly when dealing with numbers that cannot be precisely represented in binary floating-point arithmetic.

Example 1: Simple Program

Python 

from decimal import Decimal

a = 1.1 + 2.2
b = Decimal("1.1") + Decimal("2.2")

print("Float result:", a)
print("Decimal result:", b)

Output

 
OUTPUT  :
Float result: 3.3000000000000003
Decimal result: 3.3

Example 2: Advanced Program

Python 

from decimal import Decimal, getcontext

# Set the precision for Decimal operations (e.g., 50 digits)
getcontext().prec = 50

# Demonstrate float precision issues
print("--- Float Precision Demonstration ---")
float_sum = 0.1 + 0.1 + 0.1
print(f"0.1 + 0.1 + 0.1 (float): {float_sum}")
print(f"Is float_sum == 0.3? {float_sum == 0.3}")

# Demonstrate Decimal precision
print("\n--- Decimal Precision Demonstration ---")
decimal_sum = Decimal('0.1') + Decimal('0.1') + Decimal('0.1')
print(f"Decimal('0.1') + Decimal('0.1') + Decimal('0.1'): {decimal_sum}")
print(f"Is decimal_sum == Decimal('0.3')? {decimal_sum == Decimal('0.3')}")

# Further illustrate with a division
print("\n--- Division Example ---")
float_division = 1 / 3
print(f"1 / 3 (float): {float_division}")

decimal_division = Decimal(1) / Decimal(3)
print(f"Decimal(1) / Decimal(3): {decimal_division}")

# Note: Directly converting a float to Decimal can carry over float's imprecision
print("\n--- Float to Decimal Conversion ---")
imprecise_decimal = Decimal(0.1)
print(f"Decimal(0.1) (from float): {imprecise_decimal}")

Output

 
OUTPUT  :
--- Float Precision Demonstration ---
0.1 + 0.1 + 0.1 (float): 0.30000000000000004
Is float_sum == 0.3? False

--- Decimal Precision Demonstration ---
Decimal('0.1') + Decimal('0.1') + Decimal('0.1'): 0.3
Is decimal_sum == Decimal('0.3')? True

--- Division Example ---
1 / 3 (float): 0.3333333333333333
Decimal(1) / Decimal(3): 0.33333333333333333333333333333333333333333333333333

--- Float to Decimal Conversion ---
Decimal(0.1) (from float): 0.1000000000000000055511151231257827021181583404541015625

=== Code Execution Successful ===
Previous
Next