Python Day 4: Dictionaries

Dictionaries

Indexes for dictionaries are called keys. Keys are associated with a value called a key-value pair. A dictionary is unordered. Compared to a List, there is no index starting at 0.

Dictionaries are typed with braces [python]{}[/python]. To assign a dictionary to the client1 variable:

[python]client1 = {'rssi': -52, 'channel': 36, 'noise': -96, 'tx rate': 600, 'mcs': 9}[/python]

The keys within this dictionary are rssi, channel, noise, tx rate, and mcs. The values for those keys are -52, 36, 96, 600, and 9, respectively.

To access a value through a key it is performed by:

[python]
client1[‘channel’]
36
[/python]

Trying to call a key that doesn’t exist in the dictionary will result in a KeyError error message.

[python]
client1['bssid']
Traceback (most recent call last):
File "", line 1, in 
KeyError: 'bssid'
[/python]

With methods, values can be returned from a dictionary. Let’s say I want to print out the key and value of client1. I’ll use a for-loop to iterate through each of the key-value pairs and print them out using the items() method.

[python]
for i in client1.items():
print(i)
('rssi', -52)
('channel', 36)
('noise', -96)
('tx rate', 600)
('mcs', 9)
[/python]

If we just needed to print out the keys we would use the keys() method. Again, I’ll use the for-loop to iterate through the keys and print them out:

[python]
for k in client1.keys():
print(k)
rssi
channel
noise
tx rate
mcs
[/python]

If we wanted just the values we can do the same for-loop but call the values() method:

[python]
for v in client1.values():
print(v)
-52
36
-96
600
9
[/python]