Working with Dictionaries of Python for Network Engineers

This post is about the most common / useful things we do with Dictionaries in Python.

Adding & Removing Keys

Following is the syntax to add new Keys to a Dictionary

Removing can be done with 2 ways each way has its own use case. 1st one is using del keyword which will just remove the key with it's value.

Second method is to use pop() function. Since this method returns a value, they can be assigned to a variable to store the deleted values for later reference if needed.

Keys, Values & Items Functions

Using keys() function against a Dictionaries will get all keys out and can be assigned to a List like the following.

values() function do the same thing for values..

items() function can be used to get all key-value pairs as Tuples inside a List..

 

Iterating over Dictionaries

We can run loops over through the keys and values or both in a Dictionary using the above mentioned functions just like in Lists and they are very handy in Network Engineering related work.

Above will result the following..

You can run functions like sorted() along with the other functions above like the following if needed..

Similarly values() function is also working opting the values out of a Dictionary.

Following example shows how items() function is used to opt out all keys and values in a Dictionary.

Will result:-

Unpacking Dictionaries

You can merge 2 or more Dictionaries in to one Dictionary by this.

But you can't do this if the keys are duplicated. It will replace the values.

Nesting Dictionaries in Lists

Dictionaries can be nested inside Lists. Since the Keys cannot be duplicated, we can use 2 or more Dictionaries inside Lists to store data.

Working with Lists of Python for Network Engineers

This post is about the most common / useful things we do with Lists in Python.

Iterating over Lists

Most of the time we use FOR loops to iterate over Lists as it can do things for all the items in a List easily.

As an example, printing all values in a List can be done by the following code.

The result will be;

Another example will be to find the data types of the items in a List like the following,

The result will be;

Indexing, Counting & Slicing

This way we can target the items in a List instead of looping for all items.

You can see that the indexing starts with 0 and if given a negative value, it will start reading from the end.

0th item is "vlan5" and -1th item is "vlan15".

Len() function will tell you how many items are there..

count() function will tell you how many items are there of a specific value.

We can slice the List like the following,

list[X,Y] 

As you can see, Xth item is included and Yth item is excluded.

How about the following,

This means that the slicing starts with the 2nd item (note that 2nd item means actually the 3rd item as it starts from 0) and ends with 6th item (7th) but it will only capture with a gap of 1 (every second item)

Min & Max Functions

These functions help us to get the minimum and maximum values in the List items depending on the data type. As an example, if the List is full of numbers;

Let's see what happens when they are Strings..

It did not captured the item with the minimum / maximum number of characters instead it captured the lowest and highest ASCII character in order. "b" comes 1st than "i" or "l".

You can see as the Capital Letters comes 1st, it captured "Indonesia" this time. Let's see what happens if the numbers are put in string format.

But note that you cannot use min and max functions when the data types are mixed.

Appending, Inserting and Extending

append() function adds an item to the end of the List while insert() function inserts an item to a position you want and extend() function adds multiple items to the List. But there is a rule in using extend() function and that is you have to use an item which can be iterated means which can be run through a loop like FOR loop. Examples are another list or an String..

As you can see it adds the items to the end, let's see what will happen if we try to add an item to the list directly which means we try to use extend() function like the append() function.

It was taken as a String..

Let's see a real world example using the things so far..

Above program inspects all items in the list "ip_addresses" and put in to the list "public_ips" if those items does not contain the characters "192.168".

Popping, Removing and Clearing

pop() function can be used to remove an item from a List targeting an exact position of an item. However if the position is not specified, it will remove the last item of the list.

remove() function will be useful when you need to remove an item by the value. But it if duplicate values are there, it will only remove the 1st item it finds in the list.

Sorting Lists

sort() function comes handy when you needs to sort the values of the items in a List. This just works like the min() and max () functions as if all the items are numbers, it will sort normally and if the items are strings, it will again do the sorting based on the ASCII order.

Nested Lists

We can put a List inside of another List.

You can access the individual values of the nested List like the following..

Note:-

Since Tuples are very much same as Lists, but being immutable, some of the above functions like min(), max(), len(), count() also works with Tuples.