INTRODUCTION TO PYTHON.pptx

INTRODUCTION TO PYTHON
SUBMITTED BY: NIMRAH AFZAL

Introduction to Python
• Python is an interpreted, object-oriented, high-level programming
language
• Python's simple, easy to learn syntax emphasizes readability and
therefore reduces the cost of program maintenance.
• A standard distribution includes many modules
• Dynamic typed Source can be compiled or run just-in-time Similar to
perl, tcl, ruby

Why Python
• Python works on different platforms (Windows, Mac, Linux,
Raspberry Pi, etc).
• Python has a simple syntax similar to the English language.
• Python has syntax that allows developers to write programs with
fewer lines than some other programming languages.
• Python runs on an interpreter system, meaning that code can be
executed as soon as it is written. This means that prototyping can be
very quick.
• Python can be treated in a procedural way, an object-oriented way or
a functional way

Python Interfaces
IDLE : a cross-platform Python development
Python Win: a Windows only interface to Python
• Python Shell running 'python' from the Command Line opens this
interactive shell

IDLE — Development Environment
• IDLE helps you program in Python by
• color-coding your program code
• debugging ' auto-indent ‘
• interactive shell Python Shell
• Auto indent

Example python
Print (“Hello World”)
output:
Hello World

Python Indentation
• Indentation refers to the spaces at the beginning of a code line.
• Where in other programming languages the indentation in code is for
readability only, the indentation in Python is very important.
• Python uses indentation to indicate a block of code.
Example:
if 5 > 2:
print("Five is greater than two!")

Python Comments
• Comments can be used to explain Python code.
• Comments can be used to make the code more readable.
• Comments can be used to prevent execution when testing code
Example
#This is a comment
print("Hello, World!")

Python Variables
• Variables are containers for storing data values
• Python has no command for declaring a variable.
• A variable is created the moment you first assign a value to it
Example
x = 5
y = "John"
print(x)
print(y)

Python - Variable Names
A variable can have a short name (like x and y) or a more descriptive
name (age, carname, total_volume). Rules for Python variables:
• A variable name must start with a letter or the underscore character
• A variable name cannot start with a number
• A variable name can only contain alpha-numeric characters and
underscores (A-z, 0-9, and _ )
• Variable names are case-sensitive (age, Age and AGE are three
different variables)

Example
• Legal variable names:
myvar = "John"
my_var = "John"
_my_var = "John"
myVar = "John"
MYVAR = "John"
myvar2 = "John"

Python Variables - Assign Multiple Values
Python allows you to assign values to multiple variables in one line:
Example
x, y, z = "Orange", "Banana", "Cherry"
print(x)
print(y)
print(z)

Python - Output Variables
Python output variable function are print()
Example
x = "Python is awesome"
print(x)

Python - Global Variables
• Variables that are created outside of a function (as in all of the examples above)
are known as global variables.
• Global variables can be used by everyone, both inside of functions and outside
Example
x = "awesome"
def myfunc():
x = "fantastic"
print("Python is " + x)
myfunc()
print("Python is " + x)

Python Data Types
• In programming, data type is an important concept.
• Variables can store data of different types, and different types can do
different things.
• Python has the following data types built-in by default, in these
categories:
Text Type: str
Numeric
Types:
int, float, complex
Sequence
Types:
list, tuple, range
Mapping
Type:
dict
Set Types: set, frozenset
Boolean Type: bool

Python Numbers
• There are three Numeric types in python
• Int
• Float
• Complex
Example
x = 1 # int
y = 2.8 # float
z = 1j # complex

Python Casting
There may be times when you want to specify a type on to a variable. This
can be done with casting. Python is an object-orientated language, and as
such it uses classes to define data types, including its primitive types.
Casting in python is therefore done using constructor functions:
• int() - constructs an integer number from an integer literal, a float literal
(by removing all decimals), or a string literal (providing the string
represents a whole number)
• float() - constructs a float number from an integer literal, a float literal or a
string literal (providing the string represents a float or an integer)
• str() - constructs a string from a wide variety of data types, including
strings, integer literals and float literals

Example
Integers:
x = int(1) # x will be 1
y = int(2.8) # y will be 2
Floats:
x = float(1) # x will be 1.0
y = float(2.8) # y will be 2.8
Strings:
x = str("s1") # x will be 's1'
y = str(2) # y will be '2

Python Strings
• Strings in python are surrounded by either single quotation marks, or
double quotation marks.
• 'hello' is the same as "hello“
Assign String to a Variable
Assigning a string to a variable is done with the variable name followed
by an equal sign and the string:
Example
a = "Hello"
print(a)

Python - Slicing Strings
• You can return a range of characters by using the slice syntax.
• Specify the start index and the end index, separated by a colon, to
return a part of the string.
Example
Get the characters from position 2 to position 5 (not included):
b = "Hello, World!"
print(b[2:5])
Output
llo

Python - Modify Strings
Python has a set of built-in methods that you can use on strings.
Upper Case
Example
a = "Hello, World!"
print(a.upper())
Output
HELLO, WORLD!
Lower Case
a = "Hello, World!"
print(a.lower())
OUTPUT
Hello,world!

Python - String Concatenation
To concatenate, or combine, two strings you can use the + operator.
a = "Hello"
b = "World"
c = a + b
print(c)
Python - Format – Strings
age = 36
txt = "My name is John, and I am {}"
print(txt.format(age))
Output
My name is John, and I am 36

Python Booleans
Boolean represent true or false
Example
print(10 > 9)
print(10 == 9)
print(10 < 9)
Output
True
False
False

Python Operators
• Operators are used to perform operations on variables and values.
Example
print(10 + 5)
Output
15
Python Lists
Lists are used to store multiple items in a single variable
thislist = ["apple", "banana", "cherry"]
print(thislist)

Python - Access List Items
List items are indexed and you can access them by referring to the
index number:
Example
Print the second item of the list:
print(thislist[1])
Python - Change List Items:
To change the value of a specific item, refer to the index number:
thislist[1] = "blackcurrant"
print(thislist)

Python - Add List Items
• To add an item to the end of the list, use the append() method
thislist.append("orange")
print(thislist)
Output
['apple', 'banana', 'cherry', 'orange']

Python - Loop Lists
• You can loop through the list by using for loop
Example
Print all items in the list, one by one:
for x in thislist:
print(x)
Output
apple
banana
cherry

Using a While Loop
i = 0
while i < len(thislist):
print(thislist[i])
i = i + 1
Output
apple
banana
cherry

Python Tuples
thistuple = ("apple", "banana", "cherry")
print(thistuple)
Python - Access Tuple Items
You can access tuple items by referring to the index number, inside
square brackets:
Example
Print the second item in the tuple:
thistuple = ("apple", "banana", "cherry")
print(thistuple[1])

Python - Update Tuples
• Once a tuple is created, you cannot change its values. Tuples
are unchangeable, or immutable as it also is called.
• But there is a workaround. You can convert the tuple into a list, change the
list, and convert the list back into a tuple.
Example
Convert the tuple into a list to be able to change it:
x = ("apple", "banana", "cherry")
y = list(x)
y[1] = "kiwi"
x = tuple(y)
print(x)

Python Dictionaries
thisdict = {
"brand": "Ford",
"model": "Mustang",
"year": 1964
}
Print(thisdict)
Output
{'brand': 'Ford', 'model': 'Mustang', 'year': 1964}

Python Functions
• A function is a block of code which only runs when it is called.
• You can pass data, known as parameters, into a function.
• A function can return data as a result
Example
def my_function():
print("Hello from a function")
Output
Hello from a function

Python Lambda
• A lambda function is a small anonymous function.
• A lambda function can take any number of arguments, but can only
have one expression.
Example
x = lambda a : a + 10
print(x(5))
Output
15

Python Arrays
• Arrays are used to store multiple values in one single variable:
Example
cars = ["Ford", "Volvo", "BMW"]
Print(cars)
Output
['Ford', 'Volvo', 'BMW']

Python Classes and Objects
• Python is an object oriented programming language.
• Almost everything in Python is an object, with its properties and methods.
• A Class is like an object constructor, or a "blueprint" for creating objects
Example
class MyClass:
x = 5
p1 = MyClass()
print(p1.x)
Output
5

The __init__() Function
All classes have a function called __init__(), which is always executed when
the class is being initiated.
Example
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
p1 = Person("John", 36)
print(p1.name)
print(p1.age)
Output
John
36

Python Inheritance
• Inheritance allows us to define a class that inherits all the methods and properties from another
class.
Parent class is the class being inherited from, also called base class.
Child class is the class that inherits from another class, also called derived class.
class Person:
def __init__(self, fname, lname):
self.firstname = fname
self.lastname = lname
def printname(self):
print(self.firstname, self.lastname)
#Use the Person class to create an object, and then execute the printname method:
x = Person("John", "Doe")
x.printname()
Output
John Doe

Python Math
Python has a set of built-in math functions, including an extensive math
module, that allows you to perform mathematical tasks on numbers.
Example min,max:
x = min(5, 10, 25)
y = max(5, 10, 25)
print(x)
print(y)

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