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Python provides another composite data type called a dictionary, which is similar to a list in that it is a collection of objects. Here’s what you’ll learn in this tutorial: You’ll cover the basic characteristics of Python dictionaries and learn how to access and manage dictionary data.
- Dictionaries in Python
Python provides a composite data type called a dictionary,...
- Take The Quiz
Test your understanding of Python dictionaries. Python...
- Dictionaries in Python
- Creating A Python Dictionary
- Access and Delete A Key-Value Pair
- Using Try… Except
- Valid Dictionary Values
- Valid Dictionary Keys
- More Ways to Create A Python Dictionary
- Dictionary View Objects
- Merging Dictionaries
- Comparing Python Dictionaries
- Conclusion
Let’s look at how we can create and use a Python dictionary in the Python REPL: A dictionary is created by using curly braces. Inside these braces, we can add one or more key-value pairs. The pairs are separated by commas when adding more than one key-value pair. The first dictionary in our example associates keys (names like Jack and Pete) with va...
Now that you’ve seen how to initialize a dictionary, let’s see how we can add and remove entries to an already existing one:
If a requested key does not exist, an exception of type KeyErroris thrown: If you know data can be missing, e.g., when parsing input from the outside world, make sure to surround your code with a try ... except KeyError. I’ve explained this in detail in the best practices section of my article on try… except. In that article, I also explain the con...
You can put anything in a dictionary. You’re not limited to numbers or strings. In fact, you can put dictionaries and Python listsinside your dictionary and access the nested values in a very natural way: Python’s JSON decoding and encoding libraryuses this feature of Python when parsing more complex JSON documents. It creates nested trees of lists...
You can go pretty wild on your dictionary keys, too. The only requirement is that the key is hashable. Mutable types like lists, dictionaries, and sets won’t work and result in an error like: TypeError: unhashable type: ‘dict’. Besides this limitation, you can use all data types as a dictionary key, including native types like a tuple, float and in...
Depending on your data source, there are more advanced ways to initialize a dictionary that might come in handy.
Some built-in dictionary methods return a view object, offering a window on your dictionary’s keys and values. Before we start using such view objects, there’s an important concept you need to understand: values in a view object change as the content of the dictionary changes.
If you’re running Python 3.9 or later, you can use the newly introduced merging operator for dictionaries: If you’re still on a Python version between 3.5 and 3.9, you can merge two dictionaries using the following method:
If you need to compare two dictionaries, you can use a comparison operator like this: This looks and sounds trivial, but it’s not! A dictionary can contain objects of any type, after all! Consequently, Python has to walk through all the keys and values and individually compare them. You might wonder if a dictionary with the same keys and values ins...
You’ve learned what a Python dictionary is, how to create dictionaries, and how to use them. We’ve examined many practical use cases involving Python dictionaries with example code. If there’s still something missing, or you simply want to learn even more about dictionaries, you can head over to the official manual page at Python.org.
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Dec 10, 2010 · 25 Answers. Sorted by: 1142. Easily done in 2 steps: dictionary[new_key] = dictionary[old_key] del dictionary[old_key] Or in 1 step: dictionary[new_key] = dictionary.pop(old_key) which will raise KeyError if dictionary[old_key] is undefined. Note that this will delete dictionary[old_key]. >>> dictionary = { 1: 'one', 2:'two', 3:'three' }
Code sample
>>> dictionary = { 1: 'one', 2:'two', 3:'three' }>>> dictionary['ONE'] = dictionary.pop(1)>>> dictionary{2: 'two', 3: 'three', 'ONE': 'one'}>>> dictionary['ONE'] = dictionary.pop(1)...Dictionaries are used to store data values in key:value pairs. A dictionary is a collection which is ordered*, changeable and do not allow duplicates. As of Python version 3.7, dictionaries are ordered. In Python 3.6 and earlier, dictionaries are unordered.
A Python dictionary is a collection of items, similar to lists and tuples. However, unlike lists and tuples, each item in a dictionary is a key-value pair (consisting of a key and a value). Create a Dictionary. We create a dictionary by placing key: value pairs inside curly brackets {}, separated by commas. For example, # creating a dictionary .
Apr 9, 2024 · Dictionaries in Python is a data structure, used to store values in key:value format. This makes it different from lists, tuples, and arrays as in a dictionary each key has an associated value. Note: As of Python version 3.7, dictionaries are ordered and can not contain duplicate keys. How to Create a Dictionary.
Aug 31, 2023 · A Python dictionary is one such data structure that can store data in the form of key-value pairs - conceptually similar to a map. The values in a Python dictionary can be accessed using the keys. In this guide, we will be discussing Python dictionaries in detail.
