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REF: make indicator_name a cache_readonly #48040

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Merged
merged 1 commit into from
Aug 12, 2022
Merged

REF: make indicator_name a cache_readonly #48040

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32 changes: 17 additions & 15 deletions pandas/core/reshape/merge.py
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@
from pandas.util._decorators import (
Appender,
Substitution,
cache_readonly,
)
from pandas.util._exceptions import find_stack_level

Expand Down Expand Up @@ -651,16 +652,6 @@ def __init__(

self.indicator = indicator

self.indicator_name: str | None
if isinstance(self.indicator, str):
self.indicator_name = self.indicator
elif isinstance(self.indicator, bool):
self.indicator_name = "_merge" if self.indicator else None
else:
raise ValueError(
"indicator option can only accept boolean or string arguments"
)

if not is_bool(left_index):
raise ValueError(
f"left_index parameter must be of type bool, not {type(left_index)}"
Expand Down Expand Up @@ -753,6 +744,17 @@ def _maybe_drop_cross_column(
if cross_col is not None:
del result[cross_col]

@cache_readonly
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Aside, maybe we can use

from functools import cache (PY3.9)/ lru_cache

@property
@lru_cache(maxsize=None)/@cache
def _indicator_name(...)

in the future instead

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https://docs.python.org/3/library/functools.html#functools.cached_property

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Specific to here or replace cache_readonly in general?

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To replace cache_readonly in general. Could gain some nice benefits like cache clearing and thread safety (if I'm viewing the implementation correctly)

def _indicator_name(self) -> str | None:
if isinstance(self.indicator, str):
return self.indicator
elif isinstance(self.indicator, bool):
return "_merge" if self.indicator else None
else:
raise ValueError(
"indicator option can only accept boolean or string arguments"
)

def _indicator_pre_merge(
self, left: DataFrame, right: DataFrame
) -> tuple[DataFrame, DataFrame]:
Expand All @@ -765,7 +767,7 @@ def _indicator_pre_merge(
"Cannot use `indicator=True` option when "
f"data contains a column named {i}"
)
if self.indicator_name in columns:
if self._indicator_name in columns:
raise ValueError(
"Cannot use name of an existing column for indicator column"
)
Expand All @@ -786,13 +788,13 @@ def _indicator_post_merge(self, result: DataFrame) -> DataFrame:
result["_left_indicator"] = result["_left_indicator"].fillna(0)
result["_right_indicator"] = result["_right_indicator"].fillna(0)

result[self.indicator_name] = Categorical(
result[self._indicator_name] = Categorical(
(result["_left_indicator"] + result["_right_indicator"]),
categories=[1, 2, 3],
)
result[self.indicator_name] = result[self.indicator_name].cat.rename_categories(
["left_only", "right_only", "both"]
)
result[self._indicator_name] = result[
self._indicator_name
].cat.rename_categories(["left_only", "right_only", "both"])

result = result.drop(labels=["_left_indicator", "_right_indicator"], axis=1)
return result
Expand Down