[email protected]

1

COMP1021: PYTHON SYNTAX BOX

Contents

Basic Syntax ... 2

Modular programming ... 4

Advanced Syntax ... 5

Python – Optimisation ... 7

Python – File Handling ... 7

Control Statements ... 8

Turtle Functions – Import turtle ... 8

Turtle Functions – Event Handling ... 11

Time library – Managing python time ... 12

Random Library – Import random ... 12

(External Library) Music Functions – import pygame.midi... 12

Initialisation and Closing ... 12

L-System (Start value, Replacement rules, …) ... 13

2

Basic Syntax

I/O

Functions

print(‘<str_type>’, end=’<escape_char>’)

Output a string on the screen (Default: end=eoln)

end = End the line with escape char or other (e.g. eoln, null)

<str_type> = input(‘<string>’)

Prompt a string  Input a string Conversion

Functions

int(<string>)

Convert <string> into <integer> Convert any <simple data type> into <string>

str(<integer/float>)

ord(<character>)

Return the ASCII code of the char in decimal number system Return the char with specified ordinal value

chr(<ordinal_value>)

Arithmetic

Functions

round(<float/integer_type>, <n_decimal_places>)

return <float_type>

Round the <float_type> into float number with <n_decimal_places>

If <decimal_places> not set: Convert into integer If <decimal_places> = 0, data type remains unchanged

round(<integer_type>, <n…>)

return <integer_type>

Does nothing with <integer_type> even with <n…> greater than 0

max (<any_data_type>)

Return the max value Return the min value

max (<any_data_type>)

If <any_data_type> = <list/string/dictionary>: Ordinal value (e.g. ord(‘B’) > ord(‘A’)

If … = <dict_type>: max(<dict_type>) = max(<dict_type>.keys()),

max(<dict_type>.items()) <dict_type>.keys() Return <key>, <value>

Comments

‘’’ <anything_with_eoln_char> ‘’’

Comments in paragraph length Comments on a single line

# <anything_in_single_line>

Operators

+= (a = a + …)

Shorthand Assignment ( <operator>= ) Truncated: 不要小數點後的字

// (Division  integer), % (Mod)

(e.g.) 8.5 % 2 = 0.5 (Modulus operator: No conversion)

==, !=, >=, <=, >, <, not

Comparison Operator >>> 2.0000000000000001 == 2 True >>> 2.000000000000001 == 2 False >>> type(2/2) <class ‘float’> >>> type(2//2) <class ‘int’>

3 Precedence

(dec) () Bracket Power Unary operator Multiple operator Arithmetic operator Comparison operator Logical operator ** - * / % // + - < <= => > != == not and or True/ False

True or |<value>| > 0 (

Non-zero

)

False or <value> = 0

Break and Continue Statement

break

Current Loop Structure Current Loop

Loop Structure

continue

Current Iteration Next Iteration iteration ”continue” Statement of

Current Loop Structure

Swapping

<item_1>, <item_2>, …= <item_n>, <item_2>, …

Assign the nth value of the list on the right to the nth item of the list on the left ( ) <item>s can be of different types

<list_type_new> = <list_type_old>[ : : -1]

As <step> = -1, <start_pos> not specified = -1, <end_pos> not specified = Error

Reporting

import sys

#Recognise System Error

try:

<indent> <process>

except <Error>: <process>

else: <process>

Try Process Exception

cases Programme

except Error:

 ValueError Datatype Error

 I/O error

Reminder Quotes in Python can be “ (Double quote) or ‘ (Single quote)

They must be in pair All Replaced by indentation in Python { (Big bracket) or ; (Semi-colon) Indentation

 Indentation takes over any structural brackets  Indentation wrong  Syntax Error

Range 或 List 的 Step 定奪【沒提供】的

start or end 的 Value

Positive Step: start = 0 , end = len(<list_type>) Negative Step: start = ord(last item), end =

Pressing <Crtl+C>

4

Modular programming

Defining

functions

def <function_name> (<para_1>,

<para_2>, …):

<processes>

Define your own function, parameters Procedure Define

return <value/nothing>

Return a value and end Function

Variables: Function Variables

localized 的

Global Variable vs. Local variable

Global vs.

Local

global <global_variable>

<global_variable> can be used outside modules Local variable is limited to functions

<local_variable> = ‘’

Class

and objects

class <class_name>:

Define the Class Name.

All included function can be called by <class_name>.<fx>

def __init__ (self, <param_1>, <param_2>):

Define the initial parameters that new class objects have to provide

1st self

def <fx> (self, <param_1>, …)

Define Function 1st self

Class Functions __init__ variables

self.<var_name_n> = <param_n>

variables self.<var_name_n> Call (@Class)

<new_obj> = <class_name>(<param_1>,

<param_2>, …)

Define new object as a member of the <class_name> class

 Instance Objects (Attribute Reference) (Class obj.)

 Method Objects ( )

5

Advanced Syntax

Range (List) (Array)

range(<int_l>, <int_h+1>,

<pos_step >)

A temporary list consisting integers from <int_l> to <int_h> Step: +1 + <int_h+1> <int_l>

list(range(0, 3)) == 0, 1, 2

3 - 1

range(<int_h>, <int_l-1>,

<neg_step>)

Range from large to small, with negative step <neg_step> <list_type>[int_h] <list_type>[int_l-1]

range(<int_1>, <int_2>)

Range from <int_1> to <int_2> - 1

(e.g. of <neg_step>): ‘funny’[-1:2:-1] == ‘yn’

’funny’[-1:2:] == ‘’ ’funny’[2:-1:] == ‘nn’

[<item_0>, <item_1>, …]

Self-defined set starting with item 0 (ordinal value == 0) e.g. p == ape[1]

character == <str_type>[<ord_value>]

String is a list of characters

List and tuple

<list_type>= [<item_1>, <item_2>,…]

Items can be in different types

Enclosed by a pair of square brackets Can be modified

<tuple_type>= (<item_1>, <item_2>,…)

Items can be in different types

Enclosed by a pair of normal brackets Cannot be modified (Constant list) positive ordinal value: from 0 from left

<list_type>[0]: Leftmost item

negative ordinal value: from -1 from right

<list_type>[-1]: Rightmost item List

(Functions)

<list_type>.insert(<integer_position>,

<item>)

Insert an <item> into the <position> of the <list_type>

<list_type>.remove (<existing_item>)

Remove the <existing_item> from <list_type> String

<list_type>.append(<item>)

Append an <item> to the <list_type> _{<end_pos+1>:}

<list/string_type>[<start_pos>

:

<end_pos+1>

:

<step>]

<list_type> remains unchanged

Output an modified <list_type> with specified features

<list_type>.index(<search_item>)

6

如果沒有的話，Return: “ <search_item> is not in the list Default <index> = len(<list_type>) - 1

Dictionary = List type with <whatever_key> (not only automatically assigned integer) (When calling them, the order of all items are rearranged)

<dict_type> = {<key_1> : <value_1>,

<key_2> : <value_2>, …}

<dict_type>[<key_n>] = <value_n> <key_n>

for key, value in <dick_type>.items():

print(key, value)

Print out <key_n> (<value_n>) line by line

<dict_type>.items()

dict_items([(<key_1>, <value_1>), (<key_2>, <value_2>), …])

<dict_type>.values()

dict_values([<value_1>, <value_2>, …])

del <dict_type>[<key_n>]

Delete the item (key and value) with <key_n>

del : Can be used for any <data_type>:  Remove its memory location

Assessing Items

<dict_type>.keys()

dict_keys([<key_1>, <key_2>, <key_3>, …]) Nested List

(record) (3D structure)

<list_type>[x_axis][y_axis][z_axis]

Excel Database Record

 2D Structure Surface Datum

 3D Structure Cube Datum

String

Tuple List Tuple

char

len(<list_type>)

Return the length of the list = ord(<list_type>[-1]) + 1 (e.g.) ‘funny’[1:3] == ‘un’

<str_type>[<start_pos>

(Not ‘unn’

:

<end_pos+1>

)

:

<step>]

Default: <start_pos> == 0, <end_pos+1> == len(string_type>)，反正是最後 一個char

<string_type_1> + <string_type_2>

Text concatenation:

(e.g.) ‘fun’ + ‘kid’ == ‘funkid’

<string_type_1> * <integer>

<integer> copies of <string_type_1>: 重複而已 (e.g.) ‘fun’ * 3 == ‘funfunfun’

7

Python – Optimisation

Turtle library

turtle.undo()

Undo the previous turtle process <integer_type> can be

turtle.setundobuffer(<integer_type>)

None : undo buffer Improt sys

sys.getrecursionlimit()

Return the size of the stack for python Set the size of the stack to <integer_type>

sys.setrecursionlimit(<integer_type>)

Stack ……

Python – File Handling

Escape

characters

\t

Tab character New line character

\n

Read &

Write files

<file_var> = open(‘<filename>’, ‘r’)

‘r’: Open the <filename> file as Read-Only Mode ‘w’: Open the <filename> file as

<file_var> = open(‘<filename>’, ‘<w or wt>’)

Write Mode

‘wt’: Open the file using write + text mode

Whenever the file is opened this way, everything in the file is cleared.

<file_var>.write(<str_type>)

Write the <str_type> to the <file_var> Free up System resources

<file_var>.close()

<file_var>: Will be in _io.TextIOWrapper class (not str class)

for line in <file_var>: statement <file_var> <file_var>[<int>] <file_var>.readlines() Lines <list_type> items

Remove char (String

)

Default <char> = space character

.<l or n or …>strip <str_type>

<str_type>.strip(‘<char>’)

<str_type> <char>

<str_type>.lstrip(‘<char>’)

<str_type> <char>

<str_type>.rstrip(‘<char>’))

<str_type> <char> String

8

Control Statements

If Statement

if <condition_true> : <process>

If condition if true, run the process

elif <condition_true>: <process>

else: <process>

一定要有If Statemtn 在前（廢話）If … else if … else … While Loop

while <condition_true>: <process>

Condition == True, ”break” or condition == False

For Loop

for <simp_data_type> in <list>: <process>

<simp_data_type> _  variable (e.g.) for _ in range(10):

Integer or character = List items, List ordinal item

Turtle Functions – Import turtle

(usr_turtle:User-defined turtle)(turtle: System turtle, with all attributes accessible)

Basic

Import turtle

Import the turtle library for use Initialise the turtle on the screen

usr_turtle.reset()

Stop the turtle from further intruption

turtle.done()

Movement

usr_turtle.goto(<x_coor

>, <y_coor>)

usr_turtle.setpos(<x_co

or>, <y_coor>)

Initial position (middle) = 0, 0

Move the turtle to a specific coordinate on the screen

usr_turtle.forward(<pixels>)

Move the turtle ahead of its present direction

usr_turtle.backward(<pixe

_ls>)

Move the turtle back to the direction if its tail

usr_turtle.left(<angle>)

Rotate the turtle leftward by <angle> degrees

usr_turtle.right(<angle>)

Rotate the turtle rightward by <angle> degrees

usr_turtle.speed(<speed_i

ndex>)

0: Instant ; 1: Slow < 10: Fast Drawing

usr_turtle.width(<width

9 Set the width of lines drawn by turtle in

pixels Take up the turtle  Not drawing when moving

turtle.begin_fill()

<Start drawing>

turtle.end_fill()

Fill the shape drawn by the turtle with fill colour

usr_turtle.fillcolor(<hex/na

me>)

Set fill colour in <hex/name> colour

usr_turtle.fillcolor()

Return the present fill color

usr_turtle.color(<both_col

or>)

Set colour for both fill colour and pen colour

usr_turtle.color(<pen_col

or>, <fill_color>)

Set colour for 2 types of colours

usr_turtle.color()

pen colour and fill colour

usr_turtle.undo()

Undo the previous step as stored in the turtle stack

usr_turtle.dot(<integer_diameter>,

<colour>)

Define the dot size and drop a dot

usr_turtle.write(<str_type>, align=”<left/right/center>”,

font = (“<font_name>”, “<normal/bold/italic>”)

Write <str_type> on with the 1st _{char of <str_type> on turtle}

Geometry

usr_turtle.circle(<radius>, <angle_of_arc>)

Draw a circle with radius specified and centre at <radius> from the left of the usr_turtle.

<radius>: +ve: Centre on the left; -ve: Centre on the right

Counterclockwise ( <angle_of_arc> > 0)

Draw with <angle_of_arc>. A complete circle is 360 . Turtle Screen

Control

turtle.update()

Update the turtle screen

To be used after usr_turtle.tracer(False)

usr_turtle.clear()

Clear the drawings from <turtle>, not other turtles

usr_turtle.hideturtle()

usr_turtle.showturtle()

Turtle

turtle.tracer (<Boolean>)

usr_turtle.tracer(False): usr_turtle.tracer(True):

turtle.colormode(1.0)

1.0 : Float type, 255 : Integer Type

Set colour attributes into 0.0 ~ 1.0 format

turtle.colormode(255)

Set colour attributes into 0 ~ 255 format

Turtle Color attribute Color name Assign

turtle.bgcolor()

10 Turtle system

settings

turtle.mode(‘world’) /

turtle.mode(‘standard’)

Use the self-defined world or standard for turtle

turtle.setup(width=<screen_% or pixel>,

height=<screen_% or pixel>)

Setup the turtle screen size. For <screen%>, it means the % of the OS screen occupied by this turtle screen

turtle.setworldcoordinates(<left>, <bottom>, <right>, <top>)

Define the coordinates of the new world Recurring

functions

turtle.ontimer(<function>, <time_in_millisecond>)

Recur the function per <time_in_millisecond> infinitely Define new

turtles

usr_turtle.shape

(‘<Shape_name>’)

Predefined shapes: Arrow, Turtle, Circle, Square, Triangle, Classic

turtle.addshape

(‘<gif_image_file>’)

User defined shape can be used only after

addshape

<New_turtle> =

turtle.Turtle()

Define new turtle with name = <New_turtle>

usr_turtle.shapesize(‘<hei

ght>’, ‘<width>’)

Define the turtle size with heights and width

<turtles_list_type> = []

<turtles_list_type>.append(

turtle.Turtle()

)

Make good use of append(), instead of predefining the amount of list items (e.g.) turtles[i] = usr_turtle.Turtle()

11

Turtle Functions – Event Handling

usr_turtle.on (Mouse movement) No brackets after <event_function> (i.e. <…>(),

usr_turtle.onclick (<event_function>)

Run the <event_function> when the turtle in clicked by mouse

turtle.ontimer (<event_function>,

<timer_millisecond>)

Run the <event_function> according to the timer

usr_turtle.ondrag (<event_function>)

Run the <event_function> when users drags the turtle Move the turtle according to your mouse movement

usr_turtle.ondrag (usr_turtle.goto)

For instant update of the position, need usr_turtle.tracer(False) + usr_turtle.update()

usr_turtle.xcor()

Return the x coordinate of the turtle Return the y coordinate of the turtle

usr_turtle.ycor()

usr_turtle.on

(KB, MOUSE, clicking)

turtle.onscreenclick (<event_function>)

Run the <event_function> when the screen is clicked by mouse

turtle.onkeyrelease(<event_function>,

‘<key>’)

Run the Run the <event_function> when the <key> is released

turtle.onkeypress (<event_function>,

‘<key>’)

Run the <event_function> when the <key> is pressed

turtle.listen()

Keep listening any keyboard event

Run this like usr_turtle.done(), must-have + Program All turtle.on <event_function> + Related to : Requires def <event_function_name> (null_x, null_y)

12

Time library – Managing python time

Time halt

time.sleep(<time_in_second>)

Wait for <time_in_second> seconds to next statement

Condition: Used for delay in pressing/ leaving on/from a note Smooth

Python uptime

time.clock()

Return the uptime of python, in <float_type> second starting from 0

time.clock()

>>> 6.182458438486231 Program

Random Library – Import random

Randomise data

random.randrange(<int_l>, <int_h+1>)

Generate integers between int_l and int_h Randomise an integer between (Inclusive) integer_l and integer_h

random.randint(<int_l>, <int_h>))

Shuffling list

random.shuffle(<list_type>)

Randomise the orders of all <list_type> items Randomise a float number

random.uniform(<low, <high>)

between <low> and <high> (not inclusive)

(External Library) Music Functions – import pygame.midi

Initialisation and Closing

Import the midi module for playing music

import pygame.midi

Import the time module for time control

import time

Initialise the MIDI (playing music) module

pygame.midi.init()

Create an output to play music

output = pygame.midi.Output(

pygame.midi.get_default_output_id()

)

Close Music output

output.close()

Close the MIDI module

13 Note On/

Off

output.note_on(<pitch>, <volume>, <channel>)

Drum Channel <pitch> <instrument>

output.note_off(<pitch>, <volume>,

<channel>)

Pitch, Volume, Channel

Pitch in range(128)

Note in range(24, 108)

Channel in

range(16)

Default<channel> 0 Drum <channel> 9

Volume in range(128)

127: (For <channel> == 0)

output.set_intstrument(<instrument_code>)

Instrument code in range (0, 127)

L-System (Start value, Replacement rules, …)

Explanation

Variables = { F }

Variables that have replacement rules F: Usually represents “forward”

Constant = {+, - }

Constant that have predefined command

+: Turn left, -: Turn right

Starting string = FX+F

Initial string from further replacement Rules to replace the command char in string

Rules = F  FF-F-F++

Angle = 90

14

Appendix-Instrument

0 Acoustic Grand

Piano 8 Celesta 16 Drawbar Organ 24 Acoustic Guitar (nylon) 32 Acoustic Bass 40 Violin

1 Bright Acoustic Piano 9 Glockenspiel 17 Percussive Organ 25 Acoustic Guitar (steel) 33 Electric Bass (finger) 41 Viola 2 Electric Grand

Piano 10 Music Box 18 Rock Organ 26 Electric Guitar (jazz) 34 Electric Bass (pick) 42 Cello 3 Honky-tonk Piano 11 Vibraphone 19 Church Organ 27 Electric Guitar

(clean)

35 Fretless Bass 43 Contrabass

4 Electric Piano 1 12 Marimba 20 Reed Organ 28 Electric Guitar

(muted) 36 Slap Bass 1 44 Tremolo Strings

5 Electric Piano 2 13 Xylophone 21 Accordion 29 Overdriven Guitar 37 Slap Bass 2 45 Pizzicato Strings

6 Harpsichord 14 Tubular Bells 22 Harmonica 30 Distortion Guitar 38 Synth Bass 1 46 Orchestral Harp

7 Clavinet 15 Dulcimer 23 Tango

Accordion 31 Guitar Harmonics 39 Synth Bass 2 47 Timpani

48 String Ensemble 1 56 Trumpet 64 Soprano Sax 72 Piccolo 80 Lead 1 (square) 88 Pad 1 (new

age)

49 String Ensemble 2 57 Trombone 65 Alto Sax 73 Flute 81 Lead 2 (sawtooth) 89 Pad 2 (warm)

50 Synth Strings 1 58 Tuba 66 Tenor Sax 74 Recorder 82 Lead 3 (calliope) 90 Pad 3

(polysynth)

51 Synth Strings 2 59 Muted

Trumpet 67 Baritone Sax 75 Pan Flute 83 Lead 4 (chiff) 91 Pad 4 (choir)

52 Choir Aahs 60 French Horn 68 Oboe 76 Blown Bottle 84 Lead 5 (charang) 92 Pad 5 (bowed)

53 Voice Oohs 61 Brass Section 69 English Horn 77 Shakuhachi 85 Lead 6 (voice) 93 Pad 6 (metallic)

54 Synth Choir 62 Synth Brass 1 70 Bassoon 78 Whistle 86 Lead 7 (fifths) 94 Pad 7 (halo)

55 Orchestra Hit 63 Synth Brass 2 71 Clarinet 79 Ocarina 87 Lead 8 (bass +

lead)

95 Pad 8 (sweep)

96 FX 1 (rain) 104 Sitar 112 Tinkle Bell 120 Guitar Fret Noise

97 FX 2 (soundtrack) 105 Banjo 113 Agogo 121 Breath Noise

98 FX 3 (crystal) 106 Shamisen 114 Steel Drums 122 Seashore

99 FX 4 (atmosphere) 107 Koto 115 Woodblock 123 Bird Tweet

100 FX 5 (brightness) 108 Kalimba 116 Taiko Drum 124 Telephone Ring 101 FX 6 (goblins) 109 Bagpipe 117 Melodic Tom 125 Helicopter

102 FX 7 (echoes) 110 Fiddle 118 Synth Drum 126 Applause