"""Defines ValidateColumnStrategy Prototal & Defines a Default Implementation
The Protocol specifies 1 method - validate_column.
The default implementation leverage module level Custom Exceptions
Typical usage example:
for c in cols:
#will raise an error if insufficient
ValidateColumnStrategyDefault.validate_column_strategy(df, c).validate_column() # noqa: E501
"""
# Standard library imports
import sys
if sys.version_info >= (3, 8):
# Standard library imports
from typing import Protocol
else:
from typing_extensions import Protocol
# Third party imports
import pandas as pd
# chart_me imports
from chart_me.errors import (
ColumnAllNullError,
ColumnDoesNotExistsError,
ColumnTooManyNullsError,
)
[docs]
class ValidateColumnStrategy(Protocol):
"""Protocol Definition for ValidateColumnStrategy"""
[docs]
def validate_column(self) -> bool:
"""Only required method"""
...
[docs]
class ValidateColumnStrategyDefault:
"""Default implentation of ValidateColumnStrategy
Class is leverage to evaluate whether column selected is viable for charting
Attributes:
null_rate: A decimal indicating what percent of null entries in column is ok
"""
null_rate: float = 0.95 # default check
def __init__(self, df: pd.DataFrame, col: str, *, override_null_rate: float = 0.95):
"""Init of instance with ability to override class null_rate"""
self.df = df
self.col = col
ValidateColumnStrategyDefault.null_rate = override_null_rate
[docs]
def validate_column(self) -> bool:
"""Logic the evaluate column
Returns:
True or Raises an Error #TODO think of better strategy
Raises:
ColumnDoesNotExistsError
ColumnAllNullError
ColumnTooManyNullsError
"""
# check is exists
try:
_ = self.df[self.col]
except KeyError:
raise ColumnDoesNotExistsError(f"{self.col}")
if self.df[self.col].isnull().all():
raise ColumnAllNullError(f"{self.col}")
if (
self.df[self.col].isnull().sum() / len(self.col)
> ValidateColumnStrategyDefault.null_rate
):
raise ColumnTooManyNullsError(
null_rate=ValidateColumnStrategyDefault.null_rate
)
return True