CIS 465 Multimedia



CIS 465 Multimedia

JES (Jython Environment for Students) Tutorial -- I

General Guide to Using JES 3

More info on Python:

JES Screen:

[pic]

JES interface has 2 main areas:

• the Program Area (top part) –

o write your Jython programs here

o provides a text editor

o after typing in your program, go to File > Save Program As, using a filename with extension .py (for Python) – on my version of JES (3.0.6), a window opened up displaying the file structure under My Documents on the computer—however, you can save it anywhere

• the Command Area (bottom part)

o can type in Jython/Python commands here at the “>>>” prompt, hit Enter

o can type in names of loaded programs to be run

o commands are interpreted by Jython interpreter

Note:

Load Program Button

>>>>> IMPORTANT! >> word[-100:]

'HelpA'

>>> word[-10] # error

Traceback (most recent call last):

File "", line 1, in ?

IndexError: string index out of range

E.g.s

>>> s = "Lalapalooza"

>>> print s.count("la")

1

>>> print s.find("L") ( Note: chars in a string start at index 0!

0

>>> print s.find("pal")

4

>>> print s.rfind("zoo") ( not found

-1

>>> print s.rfind("La")

0

>>> s = "123anywhERE"

>>> print s

123anywhERE

>>> s.isdigit()

0

>>> s.isalpha()

0

>>> s = "OK"

>>> print s.isalpha()

1

>>> s = "Roses are red Violets are yellow"

>>> s.split(" ")

['Roses', 'are', 'red', 'Violets', 'are', 'yellow']

Programming Constructs in Python

Note:

Comment using “#”.

Some examples:

# this is the first comment

SPAM = 1 # and this is the second comment

# ... and now a third!

STRING = "# This is not a comment."

1. Looping

a. for command

• uses an index variable, the keyword “in” and a list

• note use of colon after the list – it signals that what comes next is a block

• commands in a block must be indented at least 2 spaces to become part of the block

E.g.

[pic]

>>> myloopa()

1

2

3

• can use range() function to generate the list

1. one arg: range(3) → range is from 0 to arg-1

2. two args; range(1,4) → range starts at 1 ends at 3

3. three args; range(1,4,2) →starts with 1, steps of 2, ends at 3

E.g.

[pic]

>>> myloopc()

0

1

***

1

2

***

1

3

5

***

1

>>>

• can use an array for the list

E.g.

for sample in getSamples(mySound):

b. while command

• takes a logical expression and executes its block as long as the logical expression is true

• note use of colon after the list after logical expression

E.g.

[pic]

>>> mywhile()

1

2

3

4

2. Selection (branching)

a. if command

• else is optional

• can nest the if commands

E.g. 1 – no else part

[pic]

>>> myifa()

Good grade

E.g. 2 – else part present

[pic]

>>> myifb()

Could be ok, we'll see

E.g. 3 – Nested if/else

[pic]

>>> myifc()

68 :should be improved

E.g. 4

Note:

• true or false task could be more than one statement

• indentation determines in what block a statement is

[pic]

>>> myifd()

75 :is OK

75 :could be any grade < 80

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