raise keyerror(key) from err pandas

stackoverflow.com › questions › 35831496 › keyerror-when-selecting-pandas-columns

Use sep=r'\s*,\s*' to parse a file where the columns may have some number of spaces preceding or following the delimiter (e.g. , ):

transactions = pd.read_csv('transactions.csv', sep=r'\s*,\s*',
                           header=0, encoding='ascii', engine='python')

Prove:

print(transactions.columns)

Output:

Index(['product_id', 'customer_id', 'store_id', 'promotion_id', 'month_of_year', 'quarter', 'the_year', 'store_sales', 'store_cost', 'unit_sales', 'fact_count'], dtype='object')

Alternatively, remove unquoted spaces in the CSV file, and use your command (unchanged).

Answer from MaxU - stand with Ukraine on Stack Overflow

Stack Overflow

stackoverflow.com › questions › 35831496 › keyerror-when-selecting-pandas-columns

python - KeyError when selecting pandas columns - Stack Overflow

Solution

The direct way to solve this is to add the parameter skipinitialspace in pd.read_csv(), for example:

pd.read_csv('transactions.csv', 
            sep=',', 
            skipinitialspace=True)

Reference: TheGrimmScientist's answer on "How can I remove extra whitespace from strings when parsing a csv file in Pandas?"

python - KeyError in Pandas for a correct key

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July 23, 2025 - When working with a pandas DataFrame, you might try to access a column using syntax like df['Gender']. But if that column doesn't actually exist in the DataFrame, pandas will throw a KeyError. ... Solution: Before trying to access a column, it’s a good practice to check if it exists using the in operator. Here's a safe way to handle it: ... import pandas as pd df = pd.DataFrame({'Name': ['Alice', 'Bob'], 'Age': [25, 30]}) print(df.columns) if 'Gender' in df.columns: print(df['Gender']) else: print("Column not exist.")

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April 18, 2025 - 🚀 Pandas KeyError is easy to fix if you understand why it happens. By now, you should have a clear idea of why KeyErrors occur and how to avoid them. In the next section, we’ll dive into step-by-step solutions to fix these errors so you can write error-free Pandas code.

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stackoverflow.com › questions › 75899742 › pandas-raise-keyerrorkey-from-err-keyerror-even-though-the-key-exists

python 3.x - Pandas raise KeyError(key) from err KeyError:, even though the key exists - Stack Overflow

con1 = df.loc[df[cond]==101][rtAvg].mean() File "C:\Program Files\PsychoPy\lib\site-packages\pandas\core\frame.py", line 3458, in __getitem__ indexer = self.columns.get_loc(key) File "C:\Program Files\PsychoPy\lib\site-packages\pandas\core\indexes\base.py", line 3363, in get_loc raise KeyError(key) from err KeyError: 'block1_trigger'

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stackoverflow.com › questions › 70944427 › raise-keyerrorkey-from-err-from-pandaspython

raise KeyError(key) from err from pandas(python) - Stack Overflow

February 1, 2022 - CopyTraceback (most recent call last): File "d:\learning\pandasprg.py", line 13, in <module> col = df['Fare'] File "C:\Users\USER\AppData\Local\Programs\Python\Python310\lib\site-packages\pandas\core\frame.py", line 3458, in __getitem__ indexer = self.columns.get_loc(key) File "C:\Users\USER\AppData\Local\Programs\Python\Python310\lib\site-packages\pandas\core\indexes\base.py", line 3363, in get_loc raise KeyError(key) from err KeyError: 'Fare'

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github.com › scikit-learn › scikit-learn › issues › 23393

KeyError raised when using pandas DataFrame in SelectFromModel.fit() · Issue #23393 · scikit-learn/scikit-learn

May 17, 2022 - There was an error while loading. Please reload this page. ... This is because there is no key==0 in the DF, this only works with numpy arrays not DataFrames. In version 1.0.2 this check was done with X.shape[1] which worked for both arrays and dataframes. This is breaking our existing code. import logging from mlxtend.classifier import LogisticRegression from sklearn.feature_selection._from_model import SelectFromModel import pandas as pd df = pd.DataFrame( [ ["c", 0, 3, 9, 5], ["d", 0, 4, 4, 6], ["d", 1, 15, 11, 7], ["c", 1, 1, 0, 9], ], columns=["a", "b", "c", "d", "e"], ) target_col = "b"

Author scikit-learn

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July 14, 2021 - 3897 """ -> 3898 loc = self._info_axis.get_loc(item) 3899 arraylike = value._values 3900 self._mgr.iset(loc, arraylike) ~/.envs/sigma/lib/python3.8/site-packages/pandas/core/indexes/base.py in get_loc(self, key, method, tolerance) 3361 return self._engine.get_loc(casted_key) 3362 except KeyError as err: -> 3363 raise KeyError(key) from err 3364 3365 if is_scalar(key) and isna(key) and not self.hasnans: KeyError: 'b' Note that when changing the line series = df.pop("b") to series = df.pop("b").copy() it works as expected.

Author pandas-dev

reddit.com › r/learnpython › keep getting keyerror in pandas when trying to change values in a column if they don't exist in a list

r/learnpython on Reddit: Keep Getting KeyError In Pandas When Trying To Change Values In A Column If They Don't Exist In A List

December 16, 2022 -

The title explains the full problem I have been facing. I am just going to leave the full code and the full error in hopes someone much smarter and experienced than myself can tell me where my f*ck up is

Thank you in advance!

import pandas as pd
import numpy as np

FilterThese = ['there is a list of about 500 emails', 'that goes here', 'but removed for privacy reasons']

df = pd.read_csv("full path to csv file here", sep=',')

## IF NOT IN LIST, CHANGE EMAIL TO NULL
datafilters = df.loc[~df['work_email'].isin(FilterThese), 'work_email'] = ''

print(df[datafilters])

the full error I am getting

PS C:\Users\myusername> & C:/Users/myusername/AppData/Local/Programs/Python/Python310/python.exe z:/Data/awesomedata/pandas-filter.py
Traceback (most recent call last):
  File "C:\Users\myusername\AppData\Local\Programs\Python\Python310\lib\site-packages\pandas\core\indexes\base.py", line 3621, in get_loc
    return self._engine.get_loc(casted_key)
  File "pandas\_libs\index.pyx", line 136, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\index.pyx", line 163, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\hashtable_class_helper.pxi", line 5198, in pandas._libs.hashtable.PyObjectHashTable.get_item
  File "pandas\_libs\hashtable_class_helper.pxi", line 5206, in pandas._libs.hashtable.PyObjectHashTable.get_item
KeyError: ''

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "z:\Data\awesomedata\pandas-filter.py", line 26, in <module>
    print(df[datafilters])
  File "C:\Users\myusername\AppData\Local\Programs\Python\Python310\lib\site-packages\pandas\core\frame.py", line 3505, in __getitem__
    indexer = self.columns.get_loc(key)
  File "C:\Users\myusername\AppData\Local\Programs\Python\Python310\lib\site-packages\pandas\core\indexes\base.py", line 3623, in get_loc
    raise KeyError(key) from err
KeyError: ''

Top answer

1 of 1

The error is in the last line. What are you hoping to do there? Are you sure you didn't just mean to do print(df)?

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reddit.com › r/learnpython › pandas dataframe: key error even though the key is already present

r/learnpython on Reddit: Pandas Dataframe: Key error even though the key is already present

December 13, 2022 -

I have created an aggregate pandas data frame using groupby() and count() in AWS Sagemaker Studio Lab.

aggregated_result_set = sets_df[['year','name']].groupby(by=['year']).count()

The aggregated_result_set is successfully created; if I'm using tail(), I can see data in it.

Sample data:

	name
year
2017	786
2018	816
2019	840
2020	674
2021	3

When I'm trying to filter the data of aggregated_result_set, on the basis of the year column, I'm getting an error.

Code for filtering:

aggregated_result_set[aggregated_result_set['year'].isin([1955, 2019])]

Error Message:

KeyError                                  Traceback (most recent call last)
File ~/.conda/envs/dev_env/lib/python3.10/site-packages/pandas/core/indexes/base.py:3803, in Index.get_loc(self, key, method, tolerance)
   3802 try:
-> 3803     return self._engine.get_loc(casted_key)
   3804 except KeyError as err:

File ~/.conda/envs/dev_env/lib/python3.10/site-packages/pandas/_libs/index.pyx:138, in pandas._libs.index.IndexEngine.get_loc()

File ~/.conda/envs/dev_env/lib/python3.10/site-packages/pandas/_libs/index.pyx:165, in pandas._libs.index.IndexEngine.get_loc()

File pandas/_libs/hashtable_class_helper.pxi:5745, in pandas._libs.hashtable.PyObjectHashTable.get_item()

File pandas/_libs/hashtable_class_helper.pxi:5753, in pandas._libs.hashtable.PyObjectHashTable.get_item()

KeyError: 'year'

The above exception was the direct cause of the following exception:

KeyError                                  Traceback (most recent call last)
Cell In [86], line 1
----> 1 aggregated_result_set[aggregated_result_set['year'].isin([1955, 2019])]

File ~/.conda/envs/dev_env/lib/python3.10/site-packages/pandas/core/frame.py:3805, in DataFrame.__getitem__(self, key)
   3803 if self.columns.nlevels > 1:
   3804     return self._getitem_multilevel(key)
-> 3805 indexer = self.columns.get_loc(key)
   3806 if is_integer(indexer):
   3807     indexer = [indexer]

File ~/.conda/envs/dev_env/lib/python3.10/site-packages/pandas/core/indexes/base.py:3805, in Index.get_loc(self, key, method, tolerance)
   3803     return self._engine.get_loc(casted_key)
   3804 except KeyError as err:
-> 3805     raise KeyError(key) from err
   3806 except TypeError:
   3807     # If we have a listlike key, _check_indexing_error will raise
   3808     #  InvalidIndexError. Otherwise we fall through and re-raise
   3809     #  the TypeError.
   3810     self._check_indexing_error(key)

KeyError: 'year'

Can anyone please let me know if the year column is in the aggregated_result_set, why I'm getting KeyError, and how I can resolve it?