Introduction to Python Part-1

One Day Workshop
on
Python
Devashish Kumar
Faculty-IT
iNurture

Programming Language
 A programming language is a notation for writing programs.
 A programming language is a computer language designed to
communicate instructions to a machine, particularly a computer.
 Programming languages can be used to create programs, to control the
behaviour of a machine or to express algorithms.
 Various programming languages are such as: c , c++ , R, java, C# , ruby , python
etc.

What is Python ?
Python is a high level programming language which is:
Interpreted
Interactive
Object-Oriented
Dynamic programming language
Open source model

WHY PYTHON ?
Python is nowadays widely used as an programming language. It has :-
 Simple syntax
 One-Line command
 English like commands(easily readable)
 Dynamically Typed
 Easily Indentable
 Intuitive data structures like tuples, sets, dictionaries,strings,lists etc

Applications of Python language
Python language used in:
– Web Development
– Database programming
– Game Development
– Scientific Computing
– Web Framework
– Molecular Biology

WHY 2.7 RELEASE AFTER 3.X ?
• Version 2.X has an awful quantity of useful libraries that haven’t been ported
to 3.X version.
• Current Linux distributions and Macs are still using 2.x as default. Some
are phasing out Python 2 as preinstalled default.
• Python 3 already broadly supports creating GUI applications, with Tkinter
,etc. in the standard library.
• Python 2.7 provides a stable and a supported base platform for production
system that have not yet been ported to Python 3.

 In Python 2.X, range() and xrange() function is used for
iterating and range() function behaves as it is a list.
 In Python 2.X, data type returned is in int,char etc.
 In python 2.X, no TypeError is raised if we try to
compare unorderable type.
 Handling exception: In python 2.X, for handling
exception in the syntax we use comma instead of ‘as’.
 In python 3.X, xrange() function is not used, it gives
name error and range doesnot behave as a list.
 In python 3.x, data type returned is in class.
 In python 3.X, TypeError is raised as warning if we try
to compare unorderable type.
 In python 3.X, for handling exception in the syntax we
use ‘as’ keyword.

 Packages like NumPy and SciPy,
Django,Flask,CherryPy and Pyramid is not
included in python 2.X.
 Integer Division: Python 2.X treats numbers that
you type without any digit after the decimal point
as integers,which can lead to some unexpected
results.
 Raising Exceptions:
 List comprehension loop variables:
 Packages like NumPy and SciPy,
Django,Flask,CherryPy and Pyramid is ported to
python 3.X .
 Python 3.X evaluates “3/2” as 1.5 by default,which
is more intuitive for programmer.
 Raising exceptions:
 List comprehension loop variables:

 Future_module: this module is used to
help in migration.
 .Next() function: Python 2.X supports
.next() function.
 Output:
 Python 2.x has two integer types: int and
long
 Future Module:
 .Next() function: Python 3.X doesn’t support
“.next()” function.
 In Python 3.x, no long integer type is
specified.

PYTHON VARIABLES
 A variable is a location in memory used to store some data.
 They are given unique names to differentiate between different memory locations.
 Don't need to declare a variable before using it.
 In Python, simply assign a value to a variable and it will exist. Don’t declare the type of the
variable.
 VARIABLE ASSIGNMENT: We use the assignment operator (=) to assign values to a variable.
 MULTIPLE ASSIGNMENT: In Python, multiple assignments can be made in a single statement.
 We can assign the same value to multiple variables at once.
Assignment
operator

NUMBERS
 Number data types store numeric values.
 They are immutable data types.
 Number objects are created when you assign a value to them.
 We can delete the reference to a number object by using the del statement.
 Syntax: del var1[,var2[,var3[...., varN]]]]
 We can delete a single object or multiple objects by using the del statement.

NUMBERS
 Integer numbers: Integers can be of any length, it is only limited by the
memory available. They are positive or negative whole numbers with no
decimal point.
 Floating point number : It is accurate up to 15 decimal places.
 Complex numbers : These are written in the form, x + yj, where x is the
real part and y is the imaginary part.
 Examples:
Integer
no:
Floating point
no:
Complex
number

EXAMPLES OF NUMBER
 In interactive mode, the last printed expression is assigned to the variable _
 Example:
 Division (/) always returns a float.
 To get an integer result, use floor division (//)
 To calculate the remainder you can use %:

NUMBERS
 Abs(): returns the absolute value of x i.e. the positive distance between x and zero.
 Ceil() : returns the ceiling value of x i.e. the smallest integer not less than x.
 EXP(): returns exponential of x: (e power x).
 Fabs(): returns the absolute value of x. fabs() is defined in math module and
works only on float and integer number.

NUMBERS
• Floor(): returns the floor of x i.e. the largest integer not greater than x.
• Log(): returns the natural logarithm of x.
• Log10(): returns base-10 logarithm of x for x > 0.
• Max(): returns the largest of its arguments
• There are many more functions that perform mathematical operations on
numbers.

Control Flow And Loops
Various control statements are:
 if and else
 Elif
For
Range
While
Break
Continue

IF AND ELSE STATEMENT
• The syntax for if statement in python are:
• For example:
if (condition): #execution of an if statement
statement1
statement2
else: #execution of an else statement
statement1
statement2
• If we use else statement without using if statement then it will raise an error.

Example of If And Else
Output:

Elif statement
• Elif statement is similar to the else if statement used in c or c++.
• Elif statement is a combination of else and if statement.
• Syntax: if (condition):
statement1
statement2
elif (condition): # elif is a combination of else if
statement3
statement4
else:
statement5
• There can be zero or more elif parts, and the else part is optional. The keyword
‘elif ‘ is short for ‘else if’, and is useful to avoid excessive indentation.

Example of Elif statement
Output:

For Statement
 The for statement in Python differs from in C or C++.
 Python’s for statement iterates over the items of any sequence , in the order that
they appear in the sequence.
 Syntax:
for i in m:
// repeat body for each item in m

Examples of For statement
Output: Output
Example 2:Example1:

Range Function
 Range function is used If we do not want to iterate over a sequence of numbers.
 Range function produces the sequences of values ie i,i+1,……….j-1 if it range(i,j).
 If range(i,j,k) then it increments by k that is i, i+k,……………………….,i+nk.
 Sequence produced by a range is not a list, use list(range(..)) to get a list.
 Why does range(i ,j) stops at j-1?
 to make it easier to process lists
 To iterate over the indices of a sequence, you can combine range() and len() as
follows:

WHILE LOOP
• While loop in Python is used to iterate over a block of code as long as the test
expression(condition) is true.
• Syntax: while condition:
statement(s) //repeat body till condition becomes false
• Loop might not ever run: When the condition is tested and the result is false then
the loop body will be skipped and the first statement after the while loop is executed.
• Example:
output:

Break Statement
 The break statement in python terminates the current loop and resumes
execution at the next statement , just like break statement in c.
 The break statement can be used in both for and while loops.
Output:

Continue Statement
• Continue statement in Python returns the control to the beginning of the while or
for loop. The continue statement rejects all the remaining statement in the current
iteration of the loop and moves the control back to the top of the loop.
Output:

Pass Statement
 The pass statement is used in Python when statement is required but you do not
want any command or code to execute.
 The pass statement is a null operation means nothing happens when it executes.
Suppose we have a loop or function that is not implemented yet , but we want to
implement it in future. They cannot have an empty body.
 Pass statement is there to create minimal classes.
 It is useful when you have created a code block but it is no longer required.
Comment statement is ignored by interpreter entirely and pass is not ignored.
 Example: output

Introduction to Python Part-1

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Introduction to Python Part-1