Learning Python: Dictionaries

Another data structure in Python are dictionaries. Dictionaries allow us to create a collection composed of key/value pairs.

Examples

person = {'name': 'Peter'}

The key can be a string, a tuple or a number. The value can be anything.

person_age = {'name': 'Peter', age: 47}

We can access the values in the above dictionary like so:

person_age['name'] # 'Peter'

person_age['age'] # 47

The get() method can also be used to retrieve the value:

person_age.get('name') # 'Peter'

We can also change the value in the following manner:

person_age['name'] = 'Tom'

The pop() method can be used to retrieve the value of a particular key and then delete the key/value pair that was just retrieved:

person_age.pop('name') # 'Tom'

The popitem() method removes the last key/value pair in a dictionary:

person_age.popitem()

We can check if a key is in a dictionary:

'age' in person_age # True

We can create a list of keys that are in the person_age dictionary using the keys() method:

print(list(person_age.keys())) # ['age']

We can also create a list of values that are in the person_age dictionary using the values() method:

print(list(person_age.values())) # [47]

A list of key/value pairs of the person_age dictionary can also be made using the items() method:

person_city = {'name': 'Sally', 'city': 'Toronto'}

print(list(person_city).items()) # [('name', 'Sally'), ('city', 'Toronto')]

We can get the length of a dictionary using the len() method:

len(person_city) # 2

We can add a new key/value pair to the person_city dictionary:

person_city['province'] = 'Ontario'

In order to delete a key/value pair, we use the del statement:

del person_city['province']

We can also make a copy of the person_city dictionary using the copy():

person_city_copy = person_city.copy()

This blog post was originally published on my blog Communicode, where I write about different tech topics.