Why Does Python Throw a 'KeyError: 'variablename''?

KeyError Explained: KeyError 'variablename'

In Python programming, a KeyError is encountered when a key is not found within a mapping (dictionary). The error message "KeyError: 'variablename'" indicates that the specified 'variablename' is not present in the dictionary.

Considering the provided code snippet:

path = meta_entry['path'].strip('/'),

The KeyError is raised because the 'path' key may not exist within the 'meta_entry' dictionary. To resolve this issue, verify the existence of the 'path' key in the 'meta_entry' dictionary using the 'in' operator. If the key does not exist, it can be added with a value or the code can handle the exception gracefully.

The official Python documentation defines KeyError as:

exception KeyError
Raised when a mapping (dictionary) key is not found in the set of existing keys.

For example:

mydict = {'a': '1', 'b': '2'}

Accessing existing keys in the dictionary returns their respective values:

mydict['a']  # returns '1'

However, attempting to access a non-existent key results in a KeyError:

mydict['c']  # raises KeyError: 'c'

To avoid KeyErrors, it is recommended to ensure that keys being accessed actually exist within the dictionary. This can be achieved by printing the dictionary contents or using the 'in' operator to check key existence.

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