Hi there,
according to the documentation, the parameter ignore_na="ignore" propagate[s] NaN values, without passing them to the mapping correspondence. (quote from https://pandas.pydata.org/docs/reference/api/pandas.Series.map.html)
It seems this only works if the mapping is a function, not a dictionary. See this test:
import pandas as pd
import numpy as np
mapping = {1: 10, np.nan: 42}
# succeeds as expected (basic simple test)
pd.testing.assert_series_equal(
pd.Series([1, np.nan, 2]).map(mapping),
pd.Series([10, 42, np.nan]),
)
# succeeds as expected, note the seemingly unnecessary lambda
pd.testing.assert_series_equal(
pd.Series([1, np.nan, 2]).map(lambda x: mapping.get(x), na_action="ignore"),
pd.Series([10, np.nan, np.nan]),
)
# remove the lambda and use the map directly
pd.testing.assert_series_equal(
pd.Series([1, np.nan, 2]).map(mapping, na_action="ignore"),
pd.Series([10, np.nan, np.nan]),
)
# Whoops!
# AssertionError: Series are different
#
# Series values are different (33.33333 %)
# [index]: [0, 1, 2]
# [left]: [10.0, 42.0, nan] <-- it did replace the nan even though na_action is ignore
# [right]: [10.0, nan, nan]
So to me it seems the na_action parameter is ignored for dictionaries but works for functions. I don't think it is a good idea to have different behaviour depending on the type of the mapping. So could this either be fixed or corrected in the documentation?
Tested with version 1.4.2, Python 3.10
(granted, np.nan as a dictionary key is actively asking for trouble...)
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.4