Python Dictionary Methods

Some Python code I read yesterday uses dictionary methods copy and update. This prompted me to test those two methods and check all other python dictionary methods.

Here is the code testing the two methods:

>>> d = {'a': 1, 'b': 2, 'c':3}
>>> d
{'a': 1, 'b': 2, 'c': 3}
>>> d1 = d
>>> d['a']=0
>>> d1
{'a': 0, 'b': 2, 'c': 3}
>>> d2 = d.copy()
>>> d['a'] = 4
>>> d1
{'a': 4, 'b': 2, 'c': 3}
>>> d2
{'a': 0, 'b': 2, 'c': 3}
>>> d2.update({'a':4, 'e':5})
>>> d2
{'a': 4, 'b': 2, 'c': 3, 'e': 5}
>>> 

Python official documentation lists dictionary methods on the Built-in Types page. The page has a seciton Mapping Types - dict which lists all dictionary methods. The notable class methods are clear, copy, fromkeys, get, items, keys, pop, popitem, setdefault, update, and values.

I found some interesting online documentation when searching for the topic.

• This blog post Copy a Python Dict with Updates has an example of copy and update methods.
• This stackoverflow Q&A discusses the same problem
• This webpage on W3schools.com has a list of python dictionary methods.
• Realpython.com has an article Dictionaries in Python which discusses the dictionary with more details.

The dictionary is so fundamental in Python and programmers should become familar with those methods.