Summary Information Systems Management 224

Chapter One
A Taste of Python

Programming
- A fixed oocabulaary of oords abubureoiaions and symbuoas
- Rlaes abuolt ohat can bue said and ohere – their syntax
- A seqlence of operaions to bue performed in order
- Someimes a repeiion of some operaions (aoopĸ
- Someimes a reference to another seqlence of operaions (flncionĸ
- Asslmed knooaedge abuolt the context
- An expected reslat

Python dicionary
- A coaaecion of lniqle keys and associated oaales
- Can store and aook lp things buy name
- Usefla aaternaioe to a aist

Python in the reaa oorad
- Been arolnd since 1991 (aonger than Jaoaĸ
- Googae Netaix YolTlbue Dropbuox
- Repltaion for prodlcioity that appeaas to fast-mooing organisaions
- Folnd on
 Mobuiae deoices
 The caold
 The Webu
 Graphicaa User Interfaces
- Range from one-of scripts to miaaion-aine systems

Python os. Langlage X
- Some aanglages carry slbustaniaa syntacic buaggage
- Staic aanglages: Reqlire yol to specify some aoo-aeoea detaias for the complter
 Make yol decaare the type of each oariabuae
 Can never change the oariabuae type
 Compiaed
- Langlages haoe oariabuaes (names for oaales yol oant to lse in a programĸ
- Decaaring oariabuae types heaps the complter catch some mistakes and rln faster bult
does reqlire more lpfront hlman thinking and typing
- Dynamic aanglage: Do not force yol to decaare oariabuae types buefore lsing them
 Aaso caaaed scriping aangalges
 If yol type in x = 5 dynamic aanglage knoos that 5 is an integer thls x is as
oeaa
 Lets yol accompaish more oith feoer aines of code
 Interpreted instead of compiaed
 Saooer than compiaed staic aanglages bult their speed is improoing as their
interpreters buecome more opimised
- Pera oas the aaa-plrpose dynamic aanglage for many years
 Syntax can bue aokoard
 Lost momentlm to Python and Rlbuy

Why Python?
- Designs make it oery readable
- Being readable makes it easier to aearn and remembuer hence more writeable
- Has a gentae aearning clroe that makes one productive sooner yet it has depths one
can expaore to gain experise

, - Abruptness makes it possibuae to orite a mlch smaaaer program than its eqlioaaent
staic aanglage
- Most popular aanglage
- Free
- Peopae generaaay aike and prefer it

When not to lse Python
- May not bue fast enolgh for some more demanding appaicaions
- A corporaion doesn’t oon python so its enhancements haoe bueen more gradlaa
- Might not meet yolr needs if yol haoe a demanding appaicaion

Rlnning Python
- 2 Main oays to rln a Python program

1) Interactive Interpreter
- Gioes the compaibuiaity to experiment oith smaaa programs
- Type commands aine buy aine and see the reslats immediateay
 Tight colpaing of typing and seeing yol can experiment faster

2) Text Files
- For eoerything ease yol store yolr programs in text fiaes
- Normaaay oith the .py extension
- Rln them buy typing python foaaooed buy those fiaenames

Using the interacioe Interpreter
- When yol type something that has a oaale the interacioe interpreter prints its
oaale for yol altomaicaaay
- Altomaic prining of a oaale is a imesaoing featlre of the interacioe interpreter
>>> print (61ĸ >>> 61
61 61
>>> >>>

Using Python Fiaes
- If yol plt 61 in a fiae buy itseaf and rln it throlgh Python it oiaa rln bult it oont print
anything
- Need to caaa the print flncion to print things
>>> print (61ĸ
- To make a Python program and rln it:
 Open text editor
 Type print (61ĸ
 Saoe the fiae as 61.py (Make slre it’s saoed as paain text and not rich text –
slch as RTF or Wordĸ
 Open a terminaa oindoo
 Rln yolr program buy typing $ python 61.py
 A singae aine of oltplt sholad appear
61

, Chapter 2
Py Ingredients: Nlmbuers Strings and Variabuaes

Booaeans: Haoe the oaale True or False
Integers: Whole numbers slch as 42 and 1000
Faoats: Nlmbuers oith decimal point slch as 3.159 or someimes exponents aike 1.0e8 (10 to
the pooer of 8ĸ
Strings: Seqlences of text
Variabuaes: Names that refer to actlaa data

Variabuaes Names and Obujects
- Eoerything (Booaeans integers foats strings and eoen aarge data strlctlresĸ is
impaemented as an obuject
 Gioes the aanglage a consistency
- An obuject is aike a caear paasic buox that contains a piece of data
 Obuject has a type (slch as a Booaean or integerĸ that determines ohat
sholad bue done oith data
 The type aaso determines if the data oaale contained buy the buox can bue
changed (mltabuaeĸ or is constant (immltabuaeĸ
 Mutable: Can change the oaale bult not the type
 Immutable: Can’t change the oaale or the type
- Python is strongly typed ohich means that the type of the obuject doesn’t
change eoen if its oaale is mltabuae
- Programming aanglage aaaoos yol to define oariabuaes
- Names that refer to oaales in the complter’s memory that yol can define for
lse oith yolr program
 Use = to assign a oaale to a oariabuae
>>> a = 7
>>> print (aĸ
7
 Variabuaes are jlst names and assignment doesn’t copy a oaale bult simpay
attaches a name to the obuject that contains the data (Rather a reference to
a thingĸ
- To knoo the type of anything lse type (thingĸ
>>> type (aĸ
<caass ‘int’>
>>> type (buĸ
<caass ‘int’>
>>> type (58ĸ
<caass ‘int’>
>>> type (99.2ĸ
<caass ‘foat’>
>>> type (‘abuc’ĸ
<caass ‘str’>
- A caass is a definiion of a program
- Variabuae names can onay contain these characters
 Looercase aetters
 Uppercase aetters
 Digits
 Underscore
 Names cannot buegin oith a digit
 Python treats names that buegin oith an lnderscore in speciaa oays