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unit_converter.py
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unit_converter.py
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import pandas as pd
from sqlalchemy import create_engine
from collections import defaultdict
from typing import List
from exceptions import ConversionError, UnitNotFoundError
class UnitConverter:
"""A Utility class that converts units of measure of ingredient dosages into the desired unit of measure
Example
---------------
c = UnitConverter()
ml_conversions = c.get_available_conversions('ml')
litres = c.convert(5, 'ml', 'l')
Attributes
---------------
conversion_dict: Dictionary containing conversion factor data pulled from db file
Methods
---------------
__load_conversion_dict()
Internal static method that transforms the data source into a nested dictionary for quick conversion factor
lookups
__can_convert(self, input_unit: str, output_unit: str)
Internal method that checks if the input units are supported and if they're able to be converted into their
output counterparts
get_units(self)
Returns list of all supported units
get_available_conversions(self, unit: str)
Retrieves list of supported/convertible units based on the input unit
convert(self, scalar: int, input_unit: str, output_unit: str)
Converts the input scalar into its desired unit of measure
"""
def __init__(self):
self.__conversion_dict = self.__load_conversion_dict()
@staticmethod
def __load_conversion_dict():
"""
Internal static method that transforms the data source into a nested dictionary for quick conversion factor
lookups
Returns:
---------------
conversion_dict(dict[dict[str]]): Nested dictionary of units and conversion factors
e.g {'g': {'kg': 0.001}, {'mg': 1000}, etc...}
"""
engine = create_engine(r"sqlite:///db/units_of_measure.db")
df = pd.read_sql('SELECT * FROM CONVERSION_FACTOR', engine)
dd = defaultdict(list)
for inp, out, ratio in zip(df['Unit_input'], df['Unit_output'], df['Conversion_ratio']):
dd[inp].append({out: ratio})
merged_dict = {}
conversion_dict = {}
for key, val in dd.items():
for v in val:
merged_dict.update(v)
conversion_dict[key] = merged_dict
merged_dict = {}
return conversion_dict
def __can_convert(self, input_unit: str, output_unit: str) -> bool:
"""
Internal method that checks if the input units are supported and if they're able to be converted into their
output counterparts
Parameters:
---------------
input_unit(str): input unit of measure
output_unit(str): Output unit of measure
Returns:
---------------
boolean True, else -> raise Exception
"""
if input_unit not in self.__conversion_dict:
raise UnitNotFoundError(f"Unit '{input_unit}' not available for conversion")
elif output_unit not in self.__conversion_dict[input_unit]:
raise ConversionError(f"Unit '{output_unit}' not an available conversion for unit '{input_unit}'")
else:
return True
def get_units(self):
"""
Returns list of all supported units
Returns:
---------------
list[str]: Sorted list of all supported units
"""
return sorted(list(self.__conversion_dict.keys()))
def get_available_conversions(self, unit: str) -> List[str]:
"""
Retrieves list of supported/convertible units based on the input unit
Parameters:
---------------
unit(str): unit of measure
Returns:
---------------
List[str]: Sorted list of supported/convertible units
"""
try:
unit_list = list(self.__conversion_dict[unit.lower()].keys())
return sorted(unit_list)
except KeyError:
raise UnitNotFoundError(f"Unit '{unit}' not available for conversion")
def convert(self, scalar: float, input_unit: str, output_unit: str) -> int:
"""
Converts the input scalar into its desired unit of measure
Parameters:
---------------
scalar(int): Scalar input
input_unit(str): Unit of measure of input scalar
output_unit(str): Unit of measure of output scalar
Returns:
---------------
output_scalar(int): Resulting scalar after conversion
"""
input_unit = input_unit.lower()
output_unit = output_unit.lower()
if self.__can_convert(input_unit, output_unit):
conversion_factor = self.__conversion_dict[input_unit][output_unit] if input_unit != output_unit else 1
output_scalar = conversion_factor * scalar
return output_scalar