# Midterm A - Fri 06, Nov 2020¶

Scientific Programming - Data Science @ University of Trento

Taking part to this exam erases any vote you had before

1. Download sciprog-ds-2020-11-06-exam.zip and extract it on your desktop.

2. Rename sciprog-ds-2020-11-06-FIRSTNAME-LASTNAME-ID folder: put your name, lastname an id number, like sciprog-ds-2020-11-06-john-doe-432432

From now on, you will be editing the files in that folder. At the end of the exam, that is what will be evaluated.

1. Edit the files following the instructions in this worksheet for each exercise.

2. When done zip and send to examina.icts.unitn.it/studente

## Music Sequencer¶

Open Jupyter and start editing this notebook exam-2020-11-06.ipynb

ABC is a popular format to write music notation in plain text files, you can see an example by openining tunes.abc with a text editor. A music sequencer is an editor software which typically displays notes as a matrix: you will parse simplified abc tunes and display their melodies in a matrix.

## 1. parse_melody¶

Write a function which given a melody as a string of notes translates it to a list of tuples:

>>> parse_melody("|A4      C2  E2 |C4      E D C2 |C3    B3    G2 |")
[(0, 8), (2, 4), (4, 4), (2, 8), (4, 2), (3, 2), (2, 4), (2, 6), (1, 6), (6, 4)]


Each melody note is followed by its duration. If no duration number is specified, we assume it is one.

Each tuple first element represents a note as a number from 0 (A) to 6 (G) and the second element is the note length in the sequencer. We assume our sequencer has a resolution of two beats per note, so for us a note A would have length 2, a note A2 a length 4, a note A3 a length 6 and so on.

• DO NOT care about spaces nor bars |, they have no meaning at all

• To get a character position, use ord python function

Show solution
[1]:


def parse_melody(melody):
raise Exception('TODO IMPLEMENT ME !')

from pprint import pprint
melody1 = "|A4      C2  E2 |C4      E D C2 |C3    B3    G2 |"
pprint(parse_melody(melody1) )

assert parse_melody("||") == []
assert parse_melody("|A|") == [(0,2)]
assert parse_melody("|A3|") == [(0,6)]
assert parse_melody("|A B|") == [(0,2), (1,2)]
assert parse_melody("|C D|") == [(2,2), (3,2)]
assert parse_melody(" | G    F  |   ") == [(6,2), (5,2)]
assert parse_melody("|D|B|") == [(3,2), (1,2)]
assert parse_melody("|D3 E4|") == [(3,6),(4,8)]
assert parse_melody("|F|A2 B|") == [(5,2),(0,4),(1,2)]
assert parse_melody("|A4      C2  E2 |C4      E D C2 |C3    B3    G2 |") == \
[(0, 8), (2, 4), (4, 4), (2, 8), (4, 2), (3, 2), (2, 4), (2, 6), (1, 6), (6, 4)]

[(0, 8), (2, 4), (4, 4), (2, 8), (4, 2), (3, 2), (2, 4), (2, 6), (1, 6), (6, 4)]


## 2. parse_tunes¶

An .abc file is a series of key:value fields. Keys are always one character long. Anything after a % is a comment and must be ignored

File tunes.abc excerpt:

[2]:

with open("tunes.abc", encoding='utf-8') as f: print(''.join(f.readlines()[0:17]))

%abc-2.1
H:Tune made in a dark algorithmic night    % history and origin in header, so replicated in all tunes!
O:Trento

X:1                      % index
T:Algorave               % title
C:The Lord of the Loop   % composer
M:4/4                    % meter
K:C                      % key
|A4      C2  E2 |C4      E D C2 |C3    B3    G2 |   % melodies can also have a comment

X:2
C:Matrix Queen
M:3/4
K:G
|F2  G4     |E4      E F|A2  B2  D2 |D3    E3   |C3    C3   |



First lines (3 in the example) are the file header, separated by tunes with a blank line.

• first line must always be ignored

• fields specified in the file header must be copied in all tunes

After the first blank line, there is the first tune:

• X is the tune index, convert it to integer

• M is the meter, convert it to a tuple of two integers

• K is the last field of metadata

• melody line has no field key, it always follows line with K and it immediately begins with a pipe: convert it to list by calling parse_melody

Following tunes are separated by blank lines

Write a function parse_tunes which parses the file and outputs a list of dictionaries, one per tune. Use provided field_names to obtain dictionary keys. Full expected db is in expected_db.py file.

DO NOT write hundreds of ifs

Special keys are listed above, all others should be treated in a generic way

DO NOT assume header always contains 'origin' and 'history'

It can contain any field, which has to be then copied in all the tunes.

Show solution
[3]:

field_names = {
'O':'origin',
'H':'history',
'X':'index',
'T':'title',
'C':'composer',
'M':'meter',
'K':'key',
}

def parse_tunes(filename):
raise Exception('TODO IMPLEMENT ME !')

tunes_db = parse_tunes('tunes.abc')
pprint(tunes_db[:2],width=150)


[{'composer': 'The Lord of the Loop',
'history': 'Tune made in a dark algorithmic night',
'index': 1,
'key': 'C',
'melody': [(0, 8), (2, 4), (4, 4), (2, 8), (4, 2), (3, 2), (2, 4), (2, 6), (1, 6), (6, 4)],
'meter': (4, 4),
'origin': 'Trento',
'title': 'Algorave'},
{'composer': 'Matrix Queen',
'history': 'Tune made in a dark algorithmic night',
'index': 2,
'key': 'G',
'melody': [(5, 4), (6, 8), (4, 8), (4, 2), (5, 2), (0, 4), (1, 4), (3, 4), (3, 6), (4, 6), (2, 6), (2, 6)],
'meter': (3, 4),
'origin': 'Trento',

[4]:

assert tunes_db[0]['history']=='Tune made in a dark algorithmic night'
assert tunes_db[0]['origin']=='Trento'
assert tunes_db[0]['index']==1
assert tunes_db[0]['title']=='Algorave'
assert tunes_db[0]['composer']=='The Lord of the Loop'
assert tunes_db[0]['meter']==(4,4)
assert tunes_db[0]['key']== 'C'
assert tunes_db[0]['melody']==\
[(0, 8), (2, 4), (4, 4), (2, 8), (4, 2), (3, 2), (2, 4), (2, 6), (1, 6), (6, 4)]
assert tunes_db[1]['history']=='Tune made in a dark algorithmic night'
assert tunes_db[1]['origin']=='Trento'
assert tunes_db[1]['index']==2
assert tunes_db[1]['composer']=='Matrix Queen'
assert tunes_db[1]['meter']==(3,4)
assert tunes_db[1]['key']== 'G'
assert tunes_db[1]['melody']==\
[(5, 4), (6, 8), (4, 8), (4, 2), (5, 2), (0, 4), (1, 4), (3, 4), (3, 6), (4, 6), (2, 6), (2, 6)]


## 3. sequencer¶

Write a function sequencer which takes a melody in text format and outputs a matrix of note events, as a list of strings.

The rows are all the notes on keyboard (we assume 7 notes without black keys) and the columns represent the duration of a note.

• a note start is marked with < character, a sustain with = character and end with >

• HINT 1: call parse_melody to obtain notes as a list of tuples (if you didn’t manage to implement it copy expected list from expected_db.py)

• HINT 2: build first a list of list of characters, and only at the very end convert to a list of strings

• HINT 3: try obtaining the note letters for first column by using ord and chr

Show solution
[5]:

def sequencer(melody):
raise Exception('TODO IMPLEMENT ME !')

from pprint import pprint
melody1 =  "|A4      C2  E2 |C4      E D C2 |C3    B3    G2  |"
exp1 = [
'A<======>                                        ',
'B                                      <====>    ',
'C        <==>    <======>    <==><====>          ',
'D                          <>                    ',
'E            <==>        <>                      ',
'F                                                ',
'G                                            <==>']

res1 = sequencer(melody1)
print('  ' + melody1)
print()
pprint(res1)
assert res1 == exp1

  |A4      C2  E2 |C4      E D C2 |C3    B3    G2  |

['A<======>                                        ',
'B                                      <====>    ',
'C        <==>    <======>    <==><====>          ',
'D                          <>                    ',
'E            <==>        <>                      ',
'F                                                ',
'G                                            <==>']

[6]:

from pprint import pprint
melody2 =  "|F2  G4     |E4      E F|A2  B2  D2 |D3    E3   |C3    C3   |"
exp2 =    ['A                        <==>                                ',
'B                            <==>                            ',
'C                                                <====><====>',
'D                                <==><====>                  ',
'E            <======><>                    <====>            ',
'F<==>                  <>                                    ',
'G    <======>                                                ']

res2 = sequencer(melody2)
print('  ' + melody2)
print()
pprint(res2)
assert res2 == exp2

  |F2  G4     |E4      E F|A2  B2  D2 |D3    E3   |C3    C3   |

['A                        <==>                                ',
'B                            <==>                            ',
'C                                                <====><====>',
'D                                <==><====>                  ',
'E            <======><>                    <====>            ',
'F<==>                  <>                                    ',
'G    <======>                                                ']


## 4. plot_tune¶

Make it fancy: write a function which takes a tune dictionary from the db and outputs a plot

• use beats as xs, remembering the shortest note has two beats

• to increase thickness, use linewidth=5 parameter

Show solution
[7]:

%matplotlib inline
import matplotlib.pyplot as plt

def plot_tune(tune):
raise Exception('TODO IMPLEMENT ME !')

plot_tune(tunes_db[0])

[ ]: