Error When Trying To Read CSV File

kaega2 · Dec-03-2021, 06:38 AM

Hello everyone,

I'm just learning Python for the first time and am going through the tutorial on Learnpython.org. I'm getting this weird error. I don't think I'm writing anything wrong. I'm guessing this is a bug in my version of Python? Should I downgrade to another version?

import pandas as pd

# cars = {'cars_per_cap': [809, 731, 588, 18, 200, 70, 45], 'country': ['United States', 'Australia', 'Japan', 'India', 'Russia', 'Morocco', 'Egypt'], 'drives_right': ['true', 'false', 'false', 'false', 'true', 'true', 'true']}

cars = pd.read_csv('cars.csv')
print(cars['country'])

Error:Traceback (most recent call last):
  File "C:\Users\kaega\AppData\Local\Programs\Python\Python310\lib\site-packages\pandas\core\indexes\base.py", line 3361, in get_loc
    return self._engine.get_loc(casted_key)
  File "pandas\_libs\index.pyx", line 76, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\index.pyx", line 108, 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

Traceback (most recent call last):
  File "c:\Users\kaega\Documents\Programming\Python Learning Environment\script.py", line 6, in <module>
    print(cars['country'])
  File "C:\Users\kaega\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\kaega\AppData\Local\Programs\Python\Python310\lib\site-packages\pandas\core\indexes\base.py", line 3363, in get_loc
    raise KeyError(key) from err
KeyError: 'country'

I'm using Python 3.10.0 downloaded from Python.org.
I'm using Visual Studio Code.
Not sure if this matters, but I do have Mingw64 installed as well.

bowlofred · Dec-03-2021, 07:20 AM

Before thinking about a bug I'd make sure the data matches your expectations.

What do you get for the following? Does it match the column names that you expect?

import pandas as pd
cars = pd.read_csv('cars.csv')
print(list(cars.keys()))

**deanhystad** · Dec-03-2021, 06:21 PM

I wrote this:

import pandas as pd

cars = pd.DataFrame({'cars_per_cap': [809, 731, 588, 18, 200, 70, 45], 'country': ['United States', 'Australia', 'Japan', 'India', 'Russia', 'Morocco', 'Egypt'], 'drives_right': ['true', 'false', 'false', 'false', 'true', 'true', 'true']})
cars.to_csv('cars.csv')
cars2 = pd.read_csv('cars.csv')
print(cars2['country'])

It produces this output:

Output:0    United States
1        Australia
2            Japan
3            India
4           Russia
5          Morocco
6            Egypt
Name: country, dtype: object

The csv file looks like this:

Output:,cars_per_cap,country,drives_right
0,809,United States,true
1,731,Australia,false
2,588,Japan,false
3,18,India,false
4,200,Russia,true
5,70,Morocco,true
6,45,Egypt,true

Not everything is necessary. and the CSV file doesn't need underscores instead of spaces. I edited the CSV file to look like this:

Output:cars per cap,country,drives right
809,United States,true
731,Australia,false
588,Japan,false
18,India,false
200,Russia,true
70,Morocco,true
45,Egypt,true

And ran this program:

import pandas as pd
print(pd.read_csv('cars.csv')['country'])

And it produced this output:

Output:0    United States
1        Australia
2            Japan
3            India
4           Russia
5          Morocco
6            Egypt
Name: country, dtype: object

I then modified the CSV file to look like this:

Output:cars per cap, country, drives right
809,United States,TRUE
731,Australia,FALSE
588,Japan,FALSE
18,India,FALSE
200,Russia,TRUE
70,Morocco,TRUE
45,Egypt,TRUE

And I get this error:

Error:Traceback (most recent call last):
  File "...", line 2, in <module>
    print(pd.read_csv('cars.csv')['country'])
  File "...\lib\site-packages\pandas\core\frame.py", line 3455, in __getitem__
    indexer = self.columns.get_loc(key)
  File "...\lib\site-packages\pandas\core\indexes\base.py", line 3363, in get_loc
    raise KeyError(key) from err
KeyError: 'country'

The dataframe keys are 'cars per cap', ' country', and ' drives right'. The blank I inserted to make the CSV file look pretty is being interpreted as a leading blank in the key name. Could this be your error?

kaega2 · Dec-03-2021, 09:10 PM

(Dec-03-2021, 06:21 PM)deanhystad Wrote: I wrote this:

import pandas as pd

cars = pd.DataFrame({'cars_per_cap': [809, 731, 588, 18, 200, 70, 45], 'country': ['United States', 'Australia', 'Japan', 'India', 'Russia', 'Morocco', 'Egypt'], 'drives_right': ['true', 'false', 'false', 'false', 'true', 'true', 'true']})
cars.to_csv('cars.csv')
cars2 = pd.read_csv('cars.csv')
print(cars2['country'])