Properties of Dictionary Keys in Python

Dictionary values have no restrictions. They can be any arbitrary Python object, either standard objects or user-defined objects. However, same is not true for the keys.

There are two important points to remember about dictionary keys −

• More than one entry per key not allowed. Which means no duplicate key is allowed. When duplicate keys encountered during assignment, the last assignment wins.

Example

Following is a simple example −

 Live Demo

#!/usr/bin/python
dict = {'Name': 'Zara', 'Age': 7, 'Name': 'Manni'}
print "dict['Name']: ", dict['Name']

Output

When the above code is executed, it produces the following result −

dict['Name']: Manni

• Keys must be immutable. Which means you can use strings, numbers or tuples as dictionary keys but something like ['key'] is not allowed.

Example

Following is a simple example −

 Live Demo

#!/usr/bin/python
dict = {['Name']: 'Zara', 'Age': 7}
print "dict['Name']: ", dict['Name']

Output

When the above code is executed, it produces the following result −

Traceback (most recent call last):
File "test.py", line 3, in <module>
dict = {['Name']: 'Zara', 'Age': 7};
TypeError: unhashable type: 'list'

Mohd Mohtashim

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Updated on: 28-Jan-2020

3K+ Views

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