Dictionaries In Python

18th February 2026 by Tanishq Chavan

Python C C++ Javascript React JS

Python Dictionaries: Comprehensive Theory

Dictionaries are used to store data values in key:value pairs. A dictionary is a collection which is ordered*, changeable, and does not allow duplicates.

1. Characteristics of Dictionaries

Ordered: As of Python version 3.7, dictionaries are ordered. In Python 3.6 and earlier, dictionaries are unordered.
Changeable: We can change, add, or remove items after the dictionary has been created.
Duplicates Not Allowed: Dictionaries cannot have two items with the same key. If you try to add a duplicate key, the new value will overwrite the old one.

2. Creating a Dictionary

Dictionaries are written with curly brackets {}, and have keys and values.

thisdict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}

dict() It is also possible to use the dict() constructor to make a dictionary.

thisdict = dict(name = "John", age = 36, country = "Norway")

3. Accessing Items

You can access the items of a dictionary by referring to its key name, inside square brackets [].

model = thisdict["model"]

get() There is also a method called get() that will give you the same result, but it returns None instead of an error if the key doesn't exist.

model = thisdict.get("model")

4. Dictionary Methods for Values/Keys

keys(): Returns a list of all the keys in the dictionary.
values(): Returns a list of all the values in the dictionary.
items(): Returns a list of tuples containing each key-value pair.

x = thisdict.keys()
y = thisdict.values()
z = thisdict.items()

5. Modifying & Adding Items

Change Value

You can change the value of a specific item by referring to its key name:

thisdict["year"] = 2018
# OR use update()
thisdict.update({"year": 2020})

Adding Items

Adding an item to the dictionary is done by using a new index key and assigning a value to it:

thisdict["color"] = "red"

6. Removing Items

pop(key): Removes the item with the specified key name.
popitem(): Removes the last inserted item.
del: The del keyword removes the item with the specified key name or deletes the dictionary entirely.
clear(): Empties the dictionary.

7. Nested Dictionaries

A dictionary can contain dictionaries, this is called nested dictionaries.

myfamily = {
  "child1" : {
    "name" : "Emil",
    "year" : 2004
  },
  "child2" : {
    "name" : "Tobias",
    "year" : 2007
  }
}

8. Dictionary Methods Table