Python - Playing with Records - Part Two

   
   
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Article Series

This article series discuss more than 30 different programming languages. Please read overview before you read any of the details.

Playing with Records Related Articles.

Table of Content
Where to Discuss?

Local Group

Preface

Goal: Continue Part One

4: Data Structure Using Named Tuple

There is other alternative data structure as well. Instead of dictionary, we can use named tuple.

Named Tuple

The declaration is simple.

import pprint
from collections import namedtuple
 
Song = namedtuple('MySong', ['title', 'tags'])
song = Song('Cantaloupe Island',
  ['60s', 'jazz'])

pprint.pprint(song)

With the result as below:

❯ python 12-record.py
MySong(title='Cantaloupe Island', tags=['60s', 'jazz'])

we can examine the object shown in output result above.

Python: Two tales of dictionary

The Songs Structure

We can continue our journey to records just using dictionary. No need any complex structure.

from pprint import pprint
from collections import namedtuple
 
Song  = namedtuple('MySong', ['title', 'tags'])
songs = [
  Song('Cantaloupe Island', ['60s', 'jazz']),
  Song('Let It Be', ['60s', 'rock']),
  Song('Knockin\' on Heaven\'s Door',
    ['70s', 'rock']),
  Song('Emotion', ['70s', 'pop'])),
  Song('The River', None)
]

pprint(songs)

With the result similar as below record:

❯ python 13-songs.py
[MySong(title='Cantaloupe Island', tags=['60s', 'jazz']),
 MySong(title='Let It Be', tags=['60s', 'rock']),
 MySong(title="Knockin' on Heaven's Door", tags=['70s', 'rock']),
 MySong(title='Emotion', tags=['70s', 'pop'])),
 MySong(title='The River', tags=None)]

5: Separating Module

Again, we need to reuse the songs record multiple times, so we separate the record structure from logic.

Songs Module

The code can be shown as below:

from collections import namedtuple
 
Song  = namedtuple('MySong', ['title', 'tags'])
songs = [
  Song('Cantaloupe Island', ['60s', 'jazz']),
  Song('Let It Be', ['60s', 'rock']),
  Song('Knockin\' on Heaven\'s Door',
    ['70s', 'rock']),
  Song('Emotion', ['70s', 'pop']),
  Song('The River', None)
]

Python: The Songs Module Containing List of Named Tuples

Using Songs Module

Now we can have a very short code.

from pprint import pprint
from MySongs import songs

pprint(songs)

With the result as below.

Python: Using Songs Module

❯ python 14-module.py
[{'tags': ['60s', 'jazz'], 'title': 'Cantaloupe Island'},
 {'tags': ['60s', 'rock'], 'title': 'Let It Be'},
 {'tags': ['70s', 'rock'], 'title': "Knockin' on Heaven's Door"},
 {'tags': ['70s', 'pop'], 'title': 'Emotion'},
 {'title': 'The River'}]

3: Finishing The Task

Extract, Flatten, Unique

Extracting NamedTuple

Using dot to access value

from pprint import pprint
from MyTupleSongs import songs

tagss = [
  song.tags for song in songs
  if song.tags
]

pprint(tagss)

With the result is, still list of list as shown below.

❯ python 15-extract.py
[['60s', 'jazz'], ['60s', 'rock'], ['70s', 'rock'], ['70s', 'pop'], None]

Python: Extracting Dictionary

Unique

Advance List Comprehension

Finally we solve unique list, after flattening.

from MyTupleSongs import songs

tags = [
  tag for song in songs
  if song.tags
    for tag in song.tags
]

print(list(set(tags)))

With the result similar as below array:

❯ python 17-unique.py
['pop', 'rock', '60s', '70s', 'jazz']

Python: Solving Unique Song

Also short.

What is Next 🤔?

We have alternative way to do get unique list. And we will also discuss about concurrency.

Consider continue reading [ Python - Playing with Records - Part Three ].