Avoiding common pitfalls when working with dictionaries in Python

1. Assuming a specific order when iterating over a dictionary:

Dictionaries in Python are unordered collections, and the order of iteration over their keys is not guaranteed. Therefore, assuming a specific order when iterating over a dictionary is incorrect. In this example, the keys may be printed in a different order than they were defined.

If you need to iterate over a dictionary keys in a specific order, you can sort the keys before iterating over the dictionary.

2. Assuming dictionary keys are always strings:

Dictionary keys can be of any immutable type, not just strings. In this example, the key 1 is an integer, but the code attempts to access it using a string ‘1’, which results in a KeyError because the key does not exist in the dictionary.

Ensure that the key you’re using to access a value matches the correct type of the key in the dictionary

3. Overwriting an existing key in a dictionary:

A common mistake is made when a user creates a new key-value pair with a key name which was already present in the dictionary, this can result in overwriting the previous value of that key, thereby removing the previous value completely from the dictionary and replacing it with the new value. This can also result in wrong information when user tries to access the previous old key.

If you want to update the value of an existing key without overwriting other key-value pairs, simply assign the new value to that key

4. Accessing a non-existent key without checking its existence:

When you try to access a key that does not exist in a dictionary, it raises a KeyError exception. In this example, ‘grade’ is not a key in the student dictionary, resulting in an error.

To avoid this mistake, you can use in operator to check if a key exists in the dictionary before accessing it.

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