I've been working on this project for a while: https://github.com/Mapy542/LaserOMS and have run into an issue while working on a fix for the error introduced by floating point calculations in python. I'm aware that the Python decimal module exists but it functions internally differently and this is more of an exercise of seeing if I could make the class work.
I've had issues with the Decimal class I've created. It holds a number in scientific notation: a value times 10 to a power. It seems to work during unit tests I've created, but not when integrated into the rest of the code. The financial statistics page breaks down orders and expenses that are tracked into sums by month and year, and the decimal class multiplies incorrectly in some cases by moving the decimal point around. The numeric values are consistent and correct, but 7 is very different from 7000.
I've attempted to find the error but am at a loss. It seems to be within either the from string in the initializer or the add or multiply functions.
The specific instance that didn't work is 1 * 7.20 would return 72 even though the decimal class of 7.20 would be 72 * 10 ^ -1. But 1 * 13.95 = 13.95
I've included the decimal class below as well as the other statistics function. I have also linked a database file if you wish to run the whole repo. Thanks in advance
import tinydb
from tinydb.storages import MemoryStorage
db = [
{
"expense_ID": 111,
"expense_name": "LAST_EXPENSE",
"process_status": "IGNORE",
"expense_image_path": "",
},
{
"expense_name": "Hammer Stock",
"expense_quantity": "1",
"expense_unit_price": "8",
"expense_notes": "\n",
"expense_date": "12-12-2021",
"process_status": "UTILIZE",
"expense_image_path": "",
},
{
"expense_name": "Wood Resupply",
"expense_quantity": "1",
"expense_unit_price": "95",
"expense_notes": "\n",
"expense_date": "12-12-2021",
"process_status": "UTILIZE",
"expense_image_path": "",
},
{
"expense_name": "Resin Pan",
"expense_quantity": "1",
"expense_unit_price": "20",
"expense_notes": "\n",
"expense_date": "12-12-2021",
"process_status": "UTILIZE",
"expense_image_path": "",
},
{
"expense_name": "Wood Resupply",
"expense_quantity": "1",
"expense_unit_price": "350",
"expense_notes": "\n",
"expense_date": "12-12-2021",
"process_status": "UTILIZE",
"expense_image_path": "",
},
{
"expense_name": "Bandsaw",
"expense_quantity": "1",
"expense_unit_price": "250",
"expense_notes": "\n",
"expense_date": "12-12-2021",
"process_status": "UTILIZE",
"expense_image_path": "",
},
{
"expense_name": "Bandsaw Blades",
"expense_quantity": "1",
"expense_unit_price": "50",
"expense_notes": "\n",
"expense_date": "12-12-2021",
"process_status": "UTILIZE",
"expense_image_path": "",
},
{
"expense_name": "Word Clock Supplies",
"expense_quantity": "1",
"expense_unit_price": "80",
"expense_notes": "\n",
"expense_date": "12-12-2021",
"process_status": "UTILIZE",
"expense_image_path": "",
},
{
"expense_name": "1/4 Spiral Endmill",
"expense_quantity": "1",
"expense_unit_price": "20",
"expense_notes": "\n",
"expense_date": "2-12-2022",
"process_status": "UTILIZE",
"expense_image_path": "",
},
{
"expense_name": "Shipping_Label-_2878292147",
"expense_quantity": "1",
"expense_unit_price": "7.20",
"expense_notes": "\n",
"expense_date": "05-07-2023",
"expense_image_path": "\\\\10.0.0.104\\LeboeufLasing\\09-LaserOMS\\LaserOMS-Images\\Shipping_Label-_2878292147.pdf",
"process_status": "UTILIZE",
},
{
"expense_name": "Shipping_Label-_2876623213",
"expense_quantity": "1",
"expense_unit_price": "7.20",
"expense_notes": "\n",
"expense_date": "05-07-2023",
"expense_image_path": "\\\\10.0.0.104\\LeboeufLasing\\09-LaserOMS\\LaserOMS-Images\\Shipping_Label-_2876623213.pdf",
"process_status": "UTILIZE",
},
{
"expense_name": "Shipping_Label-_2882817955",
"expense_quantity": "1",
"expense_unit_price": "13.74",
"expense_notes": "\n",
"expense_date": "05-16-2023",
"expense_image_path": "\\\\10.0.0.104\\LeboeufLasing\\09-LaserOMS\\LaserOMS-Images\\Shipping_Label-_2882817955.pdf",
"process_status": "UTILIZE",
},
{
"expense_name": "Shipping_Label-_2883954451",
"expense_quantity": "1",
"expense_unit_price": "9.59",
"expense_notes": "\n",
"expense_date": "05-16-2023",
"expense_image_path": "\\\\10.0.0.104\\LeboeufLasing\\09-LaserOMS\\LaserOMS-Images\\Shipping_Label-_2883954451.pdf",
"process_status": "UTILIZE",
},
{
"expense_name": "Lowes_more_wood_and_paint",
"expense_quantity": "1",
"expense_unit_price": "165.11",
"expense_notes": "\n\n",
"expense_date": "05-18-2023",
"expense_image_path": "\\\\10.0.0.104\\LeboeufLasing\\09-LaserOMS\\LaserOMS-Images\\Lowes_more_wood_and_paint.JPG",
"process_status": "UTILIZE",
},
{
"expense_name": "Shipping_Label-_2900550648",
"expense_quantity": "1",
"expense_unit_price": "7.00",
"expense_notes": "\n",
"expense_date": "05-26-2023",
"expense_image_path": "\\\\10.0.0.104\\LeboeufLasing\\09-LaserOMS\\LaserOMS-Images\\Shipping_Label-_2900550648.pdf",
"process_status": "UTILIZE",
},
{
"expense_name": "Shipping_Label-_2908328576",
"expense_quantity": "1",
"expense_unit_price": "7.00",
"expense_notes": "\n",
"expense_date": "05-31-2023",
"expense_image_path": "\\\\10.0.0.104\\LeboeufLasing\\09-LaserOMS\\LaserOMS-Images\\Shipping_Label-_2908328576.pdf",
"process_status": "UTILIZE",
},
{
"expense_name": "Shipping_Label-_2909910334",
"expense_quantity": "1",
"expense_unit_price": "7.00",
"expense_notes": "\n",
"expense_date": "05-31-2023",
"expense_image_path": "\\\\10.0.0.104\\LeboeufLasing\\09-LaserOMS\\LaserOMS-Images\\Shipping_Label-_2909910334.pdf",
"process_status": "UTILIZE",
},
]
class Decimal: # Replacement for a float that has no floating point error
def __init__(self, Number=0):
"""
Args:
Number (Int, String, Decimal): Number to be held as a decimal)
"""
self.value = 0 # Holds the value of the decimal
self.power = 0 # Holds the power of the decimal ie value * 10^power
if type(Number) == int:
self.value = Number
elif type(Number) == str:
if "." in Number:
while Number[-1] == "0": # Remove trailing zeros
Number = Number[:-1] # Remove last digit
self.power = (
Number.index(".") - len(Number) + 1
) # Negative power as decimal is less than 1
self.value = int(Number.replace(".", ""))
else:
self.value = int(Number)
print(self.value, self.power)
elif type(Number) == Decimal:
self.value = Number.value
self.power = Number.power
elif type(Number) == float:
StringFloat = str(Number)
if "." in StringFloat:
self.value = int(StringFloat.replace(".", ""))
self.power = StringFloat.index(".") - len(StringFloat) + 1
else:
self.value = int(StringFloat)
else:
print(Number)
raise TypeError # If the type is not supported raise an error
self.Simplify() # Simplify the decimal
def Simplify(self):
"""Simplifies the decimal by removing trailing zeros
Returns:
Decimal: Simplified decimal
"""
if self.value == 0: # If the value is 0 the power is 0
self.power = 0
return self
while self.value % 10 == 0:
self.value /= 10
self.power += 1
self.value = int(self.value)
return self
def __str__(self) -> str: # Returns the decimal as a string
Digits = []
for i in range(len(str(abs(self.value)))):
Digits.append(str(self.get_digit(self.value, i)))
if self.value < 0:
Digits.insert(0, "-")
if self.power < 0:
Digits.insert(len(Digits) + self.power, ".")
return "".join(Digits)
def __float__(self) -> float: # Returns the decimal as a float
return float(self.value * 10**self.power)
def __int__(self) -> int: # Returns the decimal as an int
return int(self.value * 10**self.power)
def get_digit(self, number, n):
"""Returns the nth digit of a number
Args:
number (int): Number to get the digit from
n (int): Digit to get
Returns:
int: nth digit of number
"""
if n < 0:
raise IndexError # If n is negative raise an error
if n >= len(str(abs(number))):
raise IndexError # If n is greater than the number of digits in number raise an error
number = abs(
number
) # Make the number positive so that the index does not include a negative sign
return int(str(number)[n])
def add(self, Number2=0):
"""Adds the value of Number2 to the value of the decimal
Args:
Number2 (Int, String, Decimal): Number to be added to the decimal
Returns:
Decimal: Decimal with the value of Number2 added to it
"""
if not type(Number2) == Decimal:
Number2 = Decimal(Number2)
if (
not self.power == Number2.power
): # If the powers are not equal make them equal by multiplying by 10^difference
if self.power > Number2.power:
self.value *= 10 ** (self.power - Number2.power)
self.power -= self.power - Number2.power
else:
Number2.value *= 10 ** (Number2.power - self.power)
self.power = Number2.power - (Number2.power - self.power)
self.value += Number2.value # Add the values
self.Simplify() # Simplify the decimal
# return self
def subtract(self, Number2=0):
"""Subtracts the value of Number2 from the value of the decimal
Args:
Number2 (Int, String, Decimal): Number to be subtracted from the decimal
Returns:
Decimal: Decimal with the value of Number2 subtracted from it
"""
if not type(Number2) == Decimal:
Number2 = Decimal(Number2)
if (
not self.power == Number2.power
): # If the powers are not equal make them equal by multiplying by 10^difference
if self.power > Number2.power:
self.value *= 10 ** (self.power - Number2.power)
self.power -= self.power - Number2.power
else:
Number2.value *= 10 ** (Number2.power - self.power)
self.power = Number2.power - (Number2.power - self.power)
self.value -= Number2.value # Subtract the values
self.Simplify() # Simplify the decimal
# return self
def multiply(self, Number2=0):
"""Multiplies the value of the decimal by the value of Number2
Args:
Number2 (Int, String, Decimal): Number to be multiplied by the decimal
Returns:
Decimal: Decimal with the value of Number2 multiplied by it
"""
if not type(Number2) == Decimal: # If Number2 is not a decimal make it one
Number2 = Decimal(Number2)
self.value *= Number2.value # Multiply the values
self.power += Number2.power # Add the powers
print(self.value, self.power)
self.Simplify() # Simplify the decimal
# return self
def divide(self, Number2=1, Accuracy=2):
"""Divides the value of the decimal by the value of Number2
Args:
Number2 (Int, String, Decimal): Number to be divided by the decimal
Accuracy (int, optional): Number of additional decimal places to calculate past the decimals of the two numbers. Defaults to 2.
Returns:
Decimal: Decimal with the value of itself divided by Number2
"""
if not type(Number2) == Decimal: # If Number2 is not a decimal make it one
Number2 = Decimal(Number2)
if Number2.value == 0:
raise ZeroDivisionError # If Number2 is 0 raise an error
if self.value / Number2.value is int: # If the value is evenly divisible
self.value /= Number2.value
self.power -= Number2.power
self.Simplify()
return self
# Divide with accuracy given for passes of long division
ResultantDigits = [] # List of digits in the resultant decimal
Dividend = self.get_digit(
self.value, 0
) # First digit of the dividend to be divided
UsedAccuracy = 0 # Number of digits of accuracy used in loop
ExtraPower = (
-1
) # Power of the decimal to be added to the resultant decimal (is positive to show decimal place is moved x places to the left: 10^(-x))
Number1Index = (
0 # Index of the digit of the dividend that has been used in the loop
)
while UsedAccuracy < Accuracy:
if Dividend == 0: # If the dividend is 0
break # Break out of the loop as the division is complete
if (
Dividend // Number2.value >= 1
): # If the dividend is wholely divisible by the divisor
ResultantDigits.append(
Dividend // Number2.value
) # Add the result of the division to the resultant decimal
Dividend = (
Dividend % Number2.value
) # Set the dividend to the remainder of the division
else: # If the dividend is not wholely divisible by the divisor
ResultantDigits.append(0) # Add a 0 to the resultant decimal
if (
Number1Index < len(str(self.value)) - 1
): # If there are more digits of the dividend to be used
Number1Index += (
1 # Increment the index of the digit of the dividend to be used
)
Dividend *= 10 # Multiply the dividend by 10 to add the next digit
Dividend += self.get_digit(
self.value, Number1Index
) # Add the next digit of the dividend to the dividend
else: # If there are no more digits of the dividend to be used
ExtraPower += 1 # Increment the power of the decimal to be added to the resultant decimal
UsedAccuracy += (
1 # Increment the number of digits of accuracy used in the loop
)
Dividend *= 10 # Multiply the dividend by 10 to add a 0 to the dividend
OriginalValue = self.value # Store the original value of the decimal
self.value = int(
"".join(map(str, ResultantDigits))
) # Set the value of the decimal to the resultant decimal
if (
OriginalValue < 0 ^ Number2.value < 0
): # If the original value of the decimal was negative or the divisor was negative
self.value *= -1 # Make the resultant decimal negative
self.power -= (
Number2.power + ExtraPower
) # Set the power of the decimal to the resultant decimal
# return self
def MonetarySubtract(Number1, Number2):
"""Subtracts two monetary values together with correct rounding for USD. (2 decimal places)
Args:
Number1 (Int, String, Decimal(Common/Class)): First Number to be subtracted
Number2 (Int, String, Decimal(Common/Class)): Second Number to be subtracted
Returns:
Float: Difference of the two numbers
"""
if not type(Number1) == Decimal:
Number1 = Decimal(Number1)
if not type(Number2) == Decimal:
Number2 = Decimal(Number2)
Number1.subtract(Number2)
return round(Number1.__float__(), 2)
def GetExpenseStats(database):
expenses = database.table("Expenses") # load all expenses
ActiveExpenses = expenses.search((tinydb.where("process_status") == "UTILIZE"))
YearlyExpenses = {}
MonthlyExpenses = {}
for expense in ActiveExpenses: # for each expense
year = expense["expense_date"].split("-")[2] # get year
if len(year) > 4:
# cut off the time or other data included after year
year = year[: len(year) - 4]
year = int(year)
month = int(expense["expense_date"].split("-")[0]) # get month
if year not in YearlyExpenses: # add year if not in years
YearlyExpenses[year] = Decimal("0")
MonthlyExpenses[year] = {}
# add month to months if not in months
if month not in MonthlyExpenses[year]:
MonthlyExpenses[year][month] = Decimal("0")
total = Decimal(expense["expense_quantity"])
total.multiply(expense["expense_unit_price"]) # calculate total
YearlyExpenses[year].add(total) # add total to applicable
MonthlyExpenses[year][month].add(total)
print(
MonthlyExpenses[year][month],
expense["expense_name"],
month,
total.value,
total.power,
)
return YearlyExpenses, MonthlyExpenses
database = tinydb.TinyDB(storage=MemoryStorage)
database.table("Expenses").insert_multiple(db)
YearlyExpenses, MonthlyExpenses = GetExpenseStats(database)
for year in MonthlyExpenses:
for month in MonthlyExpenses[year]:
print(year, month, MonthlyExpenses[year][month])
DB file for running whole repo here. (Ignore settings conflict message): https://leboeuflasing.ddns.net/Downloads/OMS-Data.json
What an interesting problem. The bug is in your "add" and "subtract" routines.
If the current exponent is LESS than the incoming exponent, you adjust the exponent of Number2, but you never put it back. You have permanently increased the value of Number2. Perhaps you should just create a temporary. Also note that the final statement serves no purpose. A - (A - B) is equal to B.
By the same token, self.power -= self.power - Number2.power is the same as self.power = Number2.power, which is really what you want.
if self.power > Number2.power:
self.value *= 10 ** (self.power - Number2.power)
self.power -= self.power - Number2.power
else:
Number2.value *= 10 ** (Number2.power - self.power)
self.power = Number2.power - (Number2.power - self.power)