Unit1: Python Programming

1. BASICS OF PYTHON
PROGRAMMING
Prepared by
Mrs. Deepa S.Rengade
Asstt. Prof.

2. python
• Simple
– Python is a simple and minimalistic language in nature
– Reading a good python program should be like reading
English
– Its Pseudo-code nature allows one to concentrate on the
problem rather than the language
• Easy to Learn
• Free & Open source
– Freely distributed and Open source
– Maintained by the Python community
• High Level Language –memory management
• Portable – *runs on anything c code will
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3. python
• Interpreted
– You run the program straight from the source code.
– Python program Bytecode a platforms native language
– You can just copy over your code to another system and it will
auto-magically work! *with python platform
• Object-Oriented
– Simple and additionally supports procedural programming
• Extensible – easily import other code
• Embeddable –easily place your code in non-python programs
• Extensive libraries
– (i.e. reg. expressions, doc generation, CGI, ftp, web browsers,
ZIP, WAV, cryptography, etc...) (wxPython, Twisted, Python
Imaging library)
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4. python Timeline/History
• Python was conceived in the late 1980s.
– Guido van Rossum, Benevolent Dictator For Life
– Rossum is Dutch, born in Netherlands, Christmas break
bored, big fan of Monty python’s Flying Circus
– Descendant of ABC, he wrote glob() func in UNIX
– M.D. @ U of Amsterdam, worked for CWI, NIST, CNRI, Google
– Also, helped develop the ABC programming language
• In 1991 python 0.9.0 was published and reached the
masses through alt.sources
• In January of 1994 python 1.0 was released
– Functional programming tools like lambda, map, filter, and
reduce
– comp.lang.python formed, greatly increasing python’s
userbase
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5. python Timeline/History
• In 1995, python 1.2 was released.
• By version 1.4 python had several new features
– Keyword arguments (similar to those of common lisp)
– Built-in support for complex numbers
– Basic form of data-hiding through name mangling
(easily bypassed however)
• Computer Programming for Everybody (CP4E) initiative
– Make programming accessible to more people, with basic “literacy”
similar to those required for English and math skills for some jobs.
– Project was funded by DARPA
– CP4E was inactive as of 2007, not so much a concern to get
employees programming “literate”
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6. python Timeline/History
• In 2000, Python 2.0 was released.
– Introduced list comprehensions similar to Haskells
– Introduced garbage collection
• In 2001, Python 2.2 was released.
– Included unification of types and classes into one
hierarchy, making pythons object model purely
Object-oriented
– Generators were added(function-like iterator
behavior)
• Standards
– http://www.python.org/dev/peps/pep-0008/
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7. Future of Python
• One of the fastest growing language
• Huge user base and constantly growing
• Stable language that is going to stay for long
• Most preferred language of companies such
as Nokia, Youtube,Google,NASA for its easy
syntax
• High speed dynamic language
• Supports for multiple programming
paradigms.
• Has bright future ahead of it supported by
huge community of OS developers
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8. Writing& Executing first Python
Program
• Download Python from www.python.org
• Once installed, Python console can be
accessed through
– Command line and running python interpreter
– GUI Software comes with python called IDLE
• Writing program:
– Open an Editor
– write instructions
– save it with extension.py
– Run the interpreter with the commend
python program_name.py
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9. Literal Constants
• Value of literal constant directly used in program
• E.g. 7,3,9,’a’,”hello” are literal constant
• They represents itself and nothing else
• Its value cannot be changed
• Numbers:integers,long integers,floating
points,complex numbers
• String:a groupof characters,immutable
• Escape sequences
• E.g a=rings bell, f=prints form feed
character,n=newline,t=prints tab,o=octal
value,x=hex value,=backslash,’=single
quote,”=doublequote
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10. Variables and identifiers
• Variables are reserved memory locations that
stores values.
• Each variable is given appropriate name.
• variables are example of identifiers
• Identifiers are names given to identify something.
• So it can be a variable, function, class, modules
etc.
• Valid identifiers: sum,_myvar,num1,var_20,a etc.
• Invalid identifiers:1num,my-var,%check,basic
sal .
• Python is a case sensitive language.
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11. Datatypes
• Variables can hold values of different types
called datatypes.
• Numbers, strings, list, tuple, dictionary
• Initializing values to variables e.g.
a=7,code=‘a’,amt=123.45 etc.
• Multiple assignment e.g. a=b=flag=0
• Assign different values to multiple variables
simultaneously e.g. sum,a,b,msg=0,3,5,”rest”
• Multiple statements on a single line usingsemi
colon.
• Boolean: datatype in python and can have
one of two values-True or False.
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12. Input Operation and
Comments
• Input() fuction= to take input from user
• It always take input as a string
• E.g. name=input(“what is your name?”)
• E.g age=input(“enter your age:”)
• Comments are non executable statements
• Added to describe staatements of program
• Characters following the# and upto end of
line are part of comment
• E.g. print(“hello”) #to display hello
• Output: hello
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13. Reserved words
• In every programming language there are
certain words which have predefined
meaning called keywords or reserved words
cannot be used for naming identifiers.
• E.g.break,class,if,else,elif,for,from,print,retu
rn
• All the python keywords contain lowercase
letters only.
• 33 keywords in python 3.7.
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14. Indentation
• Indentation is used to define a block of
code
• Block of code begins with indentation and
ends with the first unindented line.
• Usually four white spaces are referred for
indentation.
• E.g
no=10
If(no==10):
print(“no is 10”)
Output : no is 10
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15. Operators and Expressions
• Arithmetic operators: +,-,*,/,%,**,//
• Assignment operators : =,+=,-=,*=,/=,
%=,//=, **=,&=,|=, ^=,>>=, <<=
• Comparison operators: ==,!
=,>,<,>=,<=
• Logical operators:
and –returns true if both statements are true
or- returns true if one of the statement is true
not-returns false if the result is true
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16. Operators and Expressions
• Identity operators:
is – returns true if both variables are the same object
Is not – returns true if both variables are not the same object
• Membership operators:
In – returns true if a sequence with the specified value is
present in the object
Not in-– returns true if a sequence with the specified value is
not present in the object
• Bitwise operators:
• & AND
• | OR
• ^ XOR
• ~ NOT
• << left shift
• >> right shift
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17. Expressions in Python
• An expression is combination of
value, variables and operators.
• Expression appear on the right hand
side of assignment operator.
• E.g. add=a+b
• Sub=a-b
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18. THANK YOU
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