File ~\anaconda3\Lib\site-packages\pandas\core\generic.py:1911 in _get_label_or_level_values raise KeyError(key) KeyError: 'RUT'

The error `KeyError: 'RUT'` in Python typically occurs when you're trying to access a key in a dictionary or a DataFrame that doesn't exist.

Here are a few possible reasons and solutions for this error:

### 1. Non-existent column in DataFrame

If you're trying to access a column in a DataFrame that doesn't exist, you'll get a `KeyError`. Make sure the column exists in your DataFrame before trying to access it.

```python
import pandas as pd

# Create a sample DataFrame
df = pd.DataFrame({
    'Name': ['John', 'Mary', 'David'],
    'Age': [25, 31, 42]
})

# Try to access a non-existent column
try:
    print(df['RUT'])
except KeyError as e:
    print(f"Error: {e}")
```

### 2. Non-existent index in DataFrame

If you're trying to access a row in a DataFrame using its index, but the index doesn't exist, you'll get a `KeyError`. Make sure the index exists in your DataFrame before trying to access it.

```python
import pandas as pd

# Create a sample DataFrame
df = pd.DataFrame({
    'Name': ['John', 'Mary', 'David'],
    'Age': [25, 31, 42]
}, index=['RUT1', 'RUT2', 'RUT3'])

# Try to access a non-existent index
try:
    print(df.loc['RUT4'])
except KeyError as e:
    print(f"Error: {e}")
```

### 3. Non-existent key in dictionary

If you're trying to access a key in a dictionary that doesn't exist, you'll get a `KeyError`. Make sure the key exists in your dictionary before trying to access it.

```python
# Create a sample dictionary
data = {'Name': 'John', 'Age': 25}

# Try to access a non-existent key
try:
    print(data['RUT'])
except KeyError as e:
    print(f"Error: {e}")
```

### Solution

To solve the `KeyError`, you can use the following methods:

*   Check if the key exists in the dictionary or DataFrame before trying to access it.
*   Use the `get()` method to access the value associated with a key, which returns `None` if the key doesn't exist.
*   Use the `try-except` block to catch the `KeyError` exception and handle it accordingly.

```python
import pandas as pd

# Create a sample DataFrame
df = pd.DataFrame({
    'Name': ['John', 'Mary', 'David'],
    'Age': [25, 31, 42]
})

# Try to access a non-existent column
try:
    print(df['RUT'])
except KeyError as e:
    print(f"Error: {e}")

# Use the get() method to access the value associated with a key
print(df.get('Name', 'Key not found'))

# Use the try-except block to catch the KeyError exception
try:
    print(df.loc['RUT4'])
except KeyError as e:
    print(f"Error: {e}")
```