Complete Python Programming Tutorial

1. Python Programming
Ashwin Kumar Ramaswamy

2. What are
these ?
1) Google Assistant
2) Ms. Sofia ( The Robot )
3)Cortana

3. What is essential for these
technologies ?
PROGRAMMING

4. What are
Programming and
Languages ?
⮚A programming language is a
formal language comprising a set of
instructions that produce various
kinds of output.
⮚Programming languages are used
in computer programming to
implement algorithms.

5. Here we're going to see about Python
Python is a popular programming language. It was created by Guido van
Rossum, and released in 1991.
It is used for:
Web development (server-side)
Software development
System scripting
Machine Learning, Data Science
This Photo by Unknown author is licensed under CC BY-SA.

6. 1. Installation
Install the Python IDLE using this link - https://www.python.org/downloads/
Version - python 3

7. 2. Syntax
1.It is an interpreted language, we can run our code
snippets in python shell.
2.File Extension - .py
>>> print("Hello, World!")
Hello, World!

8. 3. Python Indentation
1. Indentation refers to the spaces at the beginning of a code line.
1. Python uses indentation to indicate a block of code.
if 10> 5:
print("Ten is greater than five!")

9. Thank you for watching !
Next session,
1. Variables
2. Data types
3. Casting and Numbers.

10. Python Programming
Ashwin Kumar Ramaswamy

11. 4. Comments
1.Comments can be used to prevent execution when testing code.
2.Comments can be used to make the code more readable.
Single Line Comment - #
print("Hello, World!") #This is a comment
Multiline Comment - ‘’’
Hello World !!!
‘’’

12. 5. Data
Data is defined as facts or figures, or information that's stored in or used by a computer.
Ex:
Name: Ashwin R
Course: Information Technology

13. 6. Data Types
Data Type is the type of data
Primary Data Types - Number, String, Boolean, Float, Complex
Secondary Data Types - Set, List, Dictionary, Tuple.
Text Type: str
Numeric Types: int, float, complex
Sequence Types: list, tuple, range
Mapping Type: dict
Set Types: set, frozenset
Boolean Type: bool

14. 7. Variables
Variables are containers for storing data values.
Creating Variables
1. Python has no command for declaring a variable.
2. A variable is created the moment you first assign a value to it.
X = 5
Y = "python"
print(X)
print(Y)

15. 7.1 Variable Names
1.A variable name must start with a letter or the underscore character
2;.A variable name cannot start with a number
3.A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
4.Variable names are case-sensitive (age, Age and AGE are three different variables)

16. 7.2 Legal Names
myvar = "Ashwin"
my_var = "Ashwin"
_my_var = "Ashwin"
myVar = "Ashwin"
MYVAR = "Ashwin"
myvar2 = "Ashwin"

17. 7.3 Illegal Names
2myvar = “Ashwin”
my-var = ”Ashwin”
my var = “Ashwin”

18. 7.4 Many Values to Multiple Variables
Python allows you to assign values to multiple variables in one line
x, y, z = "Orange", "Banana", "Cherry"
print(x)
print(y)
print(z)

19. 7.5 One Value to Multiple Variables
You can assign the same value to multiple variables in one line:
x = y = z = "Orange"
print(x)
print(y)
print(z)

20. 7.6 Type of variable
Using Type() build in function, we can get the data type of the variable
>>>a= 5
>>>Type(a)
integer
>>> b=”Ashwin234”
>>>Type(b)
string

21. Thank you for watching !
Next session,
1. Input and Outputs
2. Casting
3. Keywords

22. Python Programming
Ashwin Kumar Ramaswamy

23. 8. Input
Input is the basic command or signal to the machine to perform several tasks.
Getting User Input in python
input() is the build in method to get input from user
Syntax : input(“Enter the Name:”)
int(input(“Enter the Age:”))
1. Default input data type is String.
2. To get the desired type of input, we need to do casting.

24. 9. Casting or Type Casting
If you want to specify the data type of variable, this can be done with casting.
x = str(3) # x will be '3'
y = int(3) # y will be 3
z = float(3) # z will be 3.0

25. 10. Output
Outputs are the amount of something that produced due to some operations.
The Python print statement is often used to output variables.
a=input(“Enter your Name:”) # User Input ---> Ashwin
print(a) # Prints---> Ashwin

26. 11. Keywords and Build in functions
Keywords are reserved words that having some specific meaning
Ex - print, int, bool, str, float, return, global, import, from etc.
Build in functions - These are also predefined functions, which is highly helpful to reduce the
complex tasks.
Ex - sum(), abs(), type(), def(), etc.
(Will see it elaborately in upcoming classes)

27. Data Types

28. 12. Numbers
There are three numeric types in Python
1. int
2.float
3.complex
Ex :
x = 1 # int
y = 2.8 # float
z = 1j # complex

29. 13. Strings
Strings in python are surrounded by either single quotation marks, or double quotation marks.
Ex : 'hello' is the same as "hello".

30. 13.1 Multiline String
a = """This is
Python programming Tutorial
"""
print(a)

31. 13.2 Strings are Arrays
Like many other popular programming languages, strings in Python are arrays of bytes
representing unicode characters.
However, Python does not have a character data type, a single character is simply a string with a
length of 1.
Square brackets can be used to access elements of the string.
a = "Hello, World!"
print(a[1])

32. 13.3 Looping Through a String
Since strings are arrays, we can loop through the characters in a string, with a for loop.
for x in "Ashwin":
print(x)
13.3.1 String Length
To get the length of a string, use the len() function.
a = "Hello, World!"
print(len(a))

33. 13.4 Check String
To check if a certain phrase or character is present in a string, we can use the keyword in.
txt = "The best things in life are free!"
if “free in text:
print(“Yes free word is present !”)

34. 13.5 Slicing
You can return a range of characters by using the slice syntax.
1.Specify the start index and the end index, separated by a colon, to return a part of the string.
b = "Hello, World!"
print(b[2:5])
2. Slicing from Start 3. Slice To the End
b=”Python” c=”Python”
print(b[:4]) print(b[2:])

35. 13.5.1 Negative Indexing
Use negative indexes to start the slice from the end of the string:
b = “World!"
print(b[-3:-1])

36. Thank you for watching !
Next session,
1. String Methods (Part 2)
2. Boolean Type
3. Operators

37. Python Programming
Ashwin Kumar Ramaswamy

38. 13.6. Modify Strings
1. Upper Case
a = "Hello, World!"
print(a.upper())
1. Lower Case
a = "Hello, World!"
print(a.lower())

39. 13.6.1 Remove Whitespace
Whitespace is the space before and/or after the actual text, and very often you want to remove this
space.
a = " Hello, World! "
print(a.strip())

40. 13.6.2 Replace String
a = "Hello, World!"
print(a.replace("H", "J"))

41. 13.6.3 Split String
The split() method returns a list where the text between the specified separator becomes the list
items.
a = "Hello, World!"
print(a.split(","))

42. 13.7 String Concatenation
To concatenate, or combine, two strings you can use the + operator.
a = "Hello"
b = "World"
c = a + b
print(c)

43. 13.7.1 String Format
The format() method takes the passed arguments, formats them, and places them in the string
where the placeholders {} are
age = 36
txt = "My name is John, and I am {}"
print(txt.format(age))

44. 14. Boolean
Booleans represent one of two values: True or False.
print(10 > 9)
print(10 == 9)
print(10 < 9)

45. 14.1 Evaluate Values and Variables
The bool() function allows you to evaluate any value, and give you True or False in return
x = "Hello"
y = 15
print(bool(x))
print(bool(y))

46. 15. Operators
Operators are used to perform operations on variables and values.
In the example below, we use the + operator to add together two values
a = 1+2 # + is an arithmetic operator
print(a)
if (2==2) # == is a relational operator
if 2>1 # > is a comparison operator etc .

47. Thank you for watching !
Next session,
1. Operators part 2
2. Sequential Data Types
3. List (Part 1)

48. Python Programming
Ashwin Kumar Ramaswamy

49. 15.1 Operators
Arithmetic operators
Assignment operators
Comparison operators
Logical operators
Identity operators
Membership operators
Bitwise operators

50. 15.2 Arithmetic Operator
+ Addition x + y
- Subtraction x - y
* Multiplication x * y
/ Division x / y
% Modulus x % y
** Exponentiation x ** y
// Floor division x // y

51. 15.3 Assignment Operator
= x = 5
+= x += 3
-= x -= 3
*= x *= 3
/= x /= 3
%= x %= 3
//= x //= 3
**= x **= 3
&= x &= 3

52. 15.4 Comparison Operator
== Equal x == y
!= Not equal x != y
> Greater than x > y
< Less than x < y
>= Greater than or equal to x >= y
<= Less than or equal to x <= y

53. 15.5 Logical Operators
and Returns True if both statements are true x < 5 and x < 10
or Returns True if one of the statements is true x < 5 or x < 4
not Reverse the result, returns False if the result is true not(x < 5 and x <
10)

54. 15.6 Identity Operators
Identity operators are used to compare the objects, not if they are equal, but if they are actually the
same object, with the same memory location
is Returns True if both variables are the same object x is y
is not Returns True if both variables are not the same object x is not y

55. 16.7 Membership Operator
Membership operators are used to test if a sequence is presented in an object
in Returns True if a sequence with the specified value is present in the object
Ex . x in y
not in Returns True if a sequence with the specified value is not present in the object
Ex. x not in y

56. 15.8 Bitwise Operator
Bitwise operators are used to compare (binary) numbers
& AND Sets each bit to 1 if both bits are 1
| OR Sets each bit to 1 if one of two bits is 1
^ XOR Sets each bit to 1 if only one of two bits is 1
~ NOT Inverts all the bits
<< Zero fill left shift. Shift left by pushing zeros in from the right and let the leftmost
bits fall off
>> Signed right shift. Shift right by pushing copies of the leftmost bit in from the left,
and let the rightmost bits fall off

57. Sequence Data Types

58. 16. Lists
Languages= ["Python", ”C” , ”Java”]
1.Lists are used to store multiple items in a single variable.
2.Lists are one of 4 built-in data types in Python used to store collections of data

59. 16.1 List items
1.List items are ordered, changeable, and allow duplicate values.
2.List items are indexed, the first item has index [0], the second item has index [1]
etc

60. 16.2 List length
Languages= [“Python”,”C”,”C++”,”Java”]
print(len(Languages))
16.3 List Items - Data Types
details=[“Ashwin”,21,”Chennai”,8.3,True]

61. 16.3 List() Constructor
It is also possible to use the list() constructor when creating a new list.
details = list((“Ashwin”,21,”Chennai”))

62. 16.4 List Accessing
List items are indexed and you can access them by referring to the index number
Details=[“Ashwin”,21,”Chennai”]
print(Details[0])
16.4.1 Negative Indexing
thislist = ["apple", "banana", "cherry"]
print(thislist[-1])

63. Thank you for watching !
Next session,
1. List Methods (part 2)
2. Tuples
3. Tuples Methods (Part 1)

64. Python Programming
Ashwin Kumar Ramaswamy

65. 16.5 Change List Items
thislist = ["apple", "banana", "cherry"]
thislist[1] = "blackcurrant"
print(thislist)

66. 16.6 List
thislist = ["orange", "mango", "kiwi", "pineapple", "banana"]
thislist.sort()
print(thislist)

67. 17 Tuples
Tuples are used to store multiple items in a single variable.
mytuple = ("apple", "banana", "cherry")
Tuple is one of 4 built-in data types in Python used to store collections of data, the other 3 are List,
Set, and Dictionary, all with different qualities and usage.
A tuple is a collection which is ordered and unchangeable.
Tuples are written with round brackets

68. 18. Sets
myset = {"apple", "banana", "cherry"}
Sets are used to store multiple items in a single variable.
Set is one of 4 built-in data types in Python used to store collections of data, the other 3 are
List, Tuple, and Dictionary, all with different qualities and usage.
A set is a collection which is both unordered and unindexed.
Sets are written with curly brackets.

69. 19. Dictionaries
thisdict = {
"brand": "Ford",
"model": "Mustang",
"year": 1964
}
Dictionaries are used to store data values in key:value pairs.
A dictionary is a collection which is ordered*, changeable and does not allow duplicates.

70. Control Structures

71. 19. Conditional Statements: If..elif..else
An "if statement" is written by using the if keyword.
a = 200
b = 33
if b > a:
print("b is greater than a")
elif a == b:
print("a and b are equal")
else:
print("a is greater than b")

72. 19.2 Short hand If..Else
a = 2
b = 330
print("A") if a > b else print("B")

73. 19.3 Nested IF
x = 41
if x > 10:
print("Above ten,")
if x > 20:
print("and also above 20!")
else:
print("but not above 20.")

74. 19.4 pass statement
if statements cannot be empty, but if you for some reason have an if statement with no content, put
in the pass statement to avoid getting an error.
a = 33
b = 200
if b > a:
pass

75. Thank you for watching !
Next session,
1. Looping Statement
2. OOPs

76. Python Programming
Ashwin Kumar Ramaswamy

77. 20. Loops
Python has two primitive loop commands:
while loops
for loops

78. 20.1 While Loop
With the while loop we can execute a set of statements as long as a condition is true.
Print i as long as i is less than 6:
i = 1
while i < 6:
print(i)
i += 1

79. 20.2 Break Statement
With the break statement we can stop the loop even if the while condition is true:
Example
Exit the loop when i is 3: i = 1
while i < 6:
print(i)
if i == 3:
break
i += 1

80. 20.3 For Loop
A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a
string)
fruits = ["apple", "banana", "cherry"]
for x in fruits:
print(x)

81. 20.3.1 Looping through String
Even strings are iterable objects, they contain a sequence of characters:
Example
Loop through the letters in the word "banana":
for x in "banana":
print(x)

82. 20.4 Continue Statement
With the continue statement we can stop the current iteration of the loop, and continue with the
next:
Example
Do not print banana:
fruits = ["apple", "banana", "cherry"]
for x in fruits:
if x == "banana":
continue
print(x)

83. 20.5 Range() function
To loop through a set of code a specified number of times, we can use the range() function,
range(start,stop,step)
for x in range(6):
print(x)
for x in range(2, 6):
print(x)
for x in range(2, 30, 3):
print(x)

84. 20.6 Nested Loops
A nested loop is a loop inside a loop.
The "inner loop" will be executed one time for each iteration of the "outer loop"
adj = ["red", "big", "tasty"]
fruits = ["apple", "banana", "cherry"]
for x in adj:
for y in fruits:
print(x, y)

85. 20.7 pass statement
for loops cannot be empty, but if you for some reason have a for loop with no content, put in the
pass statement to avoid getting an error.
for x in [0, 1, 2]:
pass

86. 21. 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.
Creating Function
In Python a function is defined using the def keyword:
def my_function():
print("Hello from a function")

87. 21.1 Function Call
To call a function, use the function name followed by parenthesis:
def my_function():
print("Hello from a function")
my_function()

88. 21.2 Arguments
Information can be passed into functions as arguments.
Arguments are specified after the function name, inside the parentheses. You can add as many
arguments as you want, just separate them with a comma.
def my_function(fname):
print(fname + " Refsnes")
my_function("Emil")
my_function("Tobias")
my_function("Linus")

89. Thank you for watching !
Next session,
1. Functions (part 2)
2. Anonymous Functions
3. OOPs

90. 21.2 Arbitrary Arguments
If you do not know how many arguments that will be passed into your function, add a *
before the parameter name in the function definition.
def my_function(*kids):
print("The youngest child is " + kids[2])
my_function("Emil", "Tobias", "Linus"

91. 21.3 keyword arguments
You can also send arguments with the key = value syntax
def my_function(child3, child2, child1):
print("The youngest child is " + child3)
my_function(child1 = "Emil", child2 = "Tobias", child3 = "Linus")

92. 21.4 Arbitrary Keyword Arguments,
**kwargs
If you do not know how many keyword arguments that will be passed into your function, add two
asterisk: ** before the parameter name in the function definition.
def my_function(**kid):
print("His last name is " + kid["lname"])
my_function(fname = "Tobias", lname = "Refsnes")

93. 21.5 Default Parameter Value
def my_function(country = "Norway"):
print("I am from " + country)
my_function("Sweden")
my_function("India")
my_function()
my_function("Brazil")

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

95. Object Oriented Programming

96. What is OOP ?
Object-oriented programming (OOP) is a computer programming
model that organizes software design around data, or objects,
rather than functions and logic. An object can be defined as a data
field that has unique attributes and behaviour. Additional benefits
of OOP include code reusability, scalability and efficiency.

97. Pillars of OOP
1. Encapsulation
2. Abstraction
3. Inheritance
4. Polymorphism

98. Class 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.

99. Create a Class
class MyClass:
x = 5

100. Create Object
Now we can use the class named MyClass to create objects
p1 = MyClass()
print(p1.x)

101. Thank you for watching !
Next session,
1. OOP concepts

102. Python Programming
Ashwin Kumar Ramaswamy

103. 13. __init__()
The examples above are classes and objects in their simplest form, and are not really useful in real
life applications.
To understand the meaning of classes, we have to understand the built-in __init__() function.
All classes have a function called __init__(), which is always executed when the class is being
initiated.
Use the __init__() function to assign values to object properties, or other operations that are
necessary to do when the object is being created

104. __init__() Constructor
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
p1 = Person("John", 36)
print(p1.name)
print(p1.age)

105. 13.1 Object Methods
Objects can also contain methods. Methods in objects are functions that belong to the object.
Let us create a method in the Person class
class Person:
def __init__(self, name, age):
self.name = name
self.age = age
def myfunc(self):
print("Hello my name is " + self.name)

106. 13.2 The Self Parameter
The self parameter is a reference to the current instance of the class, and is used to access
variables that belongs to the class.
It does not have to be named self , you can call it whatever you like, but it has to be the first
parameter of any function in the class

107. Ex.
class Person:
def __init__(mysillyobject, name, age):
mysillyobject.name = name
mysillyobject.age = age
def myfunc(abc):
print("Hello my name is " + abc.name)
p1 = Person("John", 36)
p1.myfunc()

108. 14. 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.

109. 14.1 Types of Inheritance
1.Single Level
2.Multilevel
3.Multiple Level

111. 14.2 Single Level Inheritance
When a class inherits another class, it is known as a
single inheritance. In the example given below, Dog
class inherits the Animal class, so there is the single
inheritance.

112. 14.3 Multilevel Inheritance
Multilevel inheritance in java with example. When a class
extends a class, which extends anther class then this is
called multilevel inheritance. For example class C
extends class B and class B extends class A then this
type of inheritance is known as multilevel inheritance.

113. 14.4 Multiple Inheritance
Multiple inheritance is a feature of some object-oriented
computer programming languages in which an object or
class can inherit characteristics and features from more
than one parent object or parent class

114. Thank you for watching !
Next session,
1. OOP concepts (Part 3)

115. 15. Encapsulation
Encapsulation in Python is the process of wrapping up
variables and methods into a single entity. In programming, a
class is an example that wraps all the variables and methods
defined inside it

116. class Car():
def __init__(self,speed,color):
self.__speed=speed
self.color=color
def get_speed(self):
return self.__speed
def set_speed(self,value):
return self.__speed
s1=Car(200,"red")
print(s1.get_speed())
print(s1.__speed)
Class

117. 16.Polymorphism
The word polymorphism means having many forms. In
programming, polymorphism means the same function name
(but different signatures) being used for different types.

118. 15.1 Method Overloading
Method overloading is a form of polymorphism in OOP. One such manner in
which the methods behave according to their argument types and number of
arguments is method overloading. Overloading happens when you have two
methods with the same name but different signatures (or arguments).

119. class Student():
def __init__(self,a,b):
self.a=a
self.b=b
def sum(self,a=None,b=None,c=None):
s=0
if(a!=None and b!=None and c!=None):
s=a+b+c
elif (a!=None and b!=None):
s=a+b
else:
s=c
return s
s1=Student(50,30)
print(s1.sum(20,30))
print(s1.sum(20,30,10))
print(s1.sum(20))

120. 15.2 Method Overriding
Method overriding is an ability of any object-oriented programming
language that allows a subclass or child class to provide a specific
implementation of a method that is already provided by one of its
super-classes or parent classes.

121. class Father:
def show(self,a,b):
print("Main")
c=a+b
print(c)
return
class Son(Father):
def show(self,a,b):
print("Subclass")
c=a+b
print(c)
return c #overrides here

122. Operator Overloading
Operator overloading in Python is the ability of a single operator to
perform more than one operation based on the class (type) of
operands. For example, the + operator can be used to add two
numbers, concatenate two strings or merge two lists.

123. 16. Recursion
The term Recursion can be defined as the process of
defining something in terms of itself. In simple words, it is
a process in which a function calls itself directly or
indirectly.

124. Recursion Example
def Recur_facto(n):
if (n == 0):
return 1
return n * Recur_facto(n-1)
print(Recur_facto(6))

125. Iteration
Iterations are performed through 'for' and 'while' loops. Iterations
execute a set of instructions repeatedly until some limiting criteria is
met. In contrast to recursion, iteration does not require temporary
memory to keep on the results of each iteration.

126. Scopes
A variable is only available from inside the region it is created. This is called scope.
Local Scope
A variable created inside a function belongs to the local scope of that function, and can only be
used inside that function.
def myfunc():
x = 300
print(x)
myfunc()

127. Function Inside Function
As explained in the example above, the variable x is not available outside the function, but it is
available for any function inside the function:
def myfunc():
x = 300
def myinnerfunc():
print(x)
myinnerfunc()
myfunc()

128. Global Scope
A variable created in the main body of the Python code is a global variable and belongs to the
global scope.
Global variables are available from within any scope, global and local.
x = 300
def myfunc():
print(x)
myfunc()
print(x)

129. Global Keyword
If you need to create a global variable, but are stuck in the local scope, you can use the global
keyword.
The global keyword makes the variable global
def myfunc():
global x
x = 300
myfunc()
print(x)

130. Modules
Consider a module to be the same as a code library.
A file containing a set of functions you want to include in your application.

131. Create a Module
To create a module, just save the code you want in a file with the file
extension .py
def greeting(name):
print("Hello, " + name)

132. Use a module
Now we can use the module we just created, by using the import statement:
import mymodule
mymodule.greeting("Jonathan")

133. Date time
A date in Python is not a data type of its own, but we can import a module
named datetime to work with dates as date objects.
import datetime
x = datetime.datetime.now()
print(x)

134. Math
Python has a set of built-in math functions, including an extensive math module,
that allows you to perform mathematical tasks on numbers.
Build in Math functions
The min() and max() functions can be used to find the lowest or highest value in
an iterable

135. Example
x = min(5, 10, 25)
y = max(5, 10, 25)
print(x)
print(y)

136. The abs() function returns the absolute (positive) value of the specified number
x = abs(-7.25)
print(x)
The pow(x, y) function returns the value of x to the power of y (x^y)
x = pow(4, 3)
print(x)

137. Math module
Python has also a built-in module called math, which extends the list of mathematical
functions.
To use it, you must import the math module
import math
x = math.sqrt(64)
print(x)

138. PIP (Python Manager for Packages)
PIP is a package manager for Python packages, or modules if you like.
What is a Package?
A package contains all the files you need for a module.
Modules are Python code libraries you can include in your project.

139. Check if PIP is Installed
Navigate your command line to the location of Python's script directory, and type the following
C:UsersYour NameAppDataLocalProgramsPythonPython36-32Scripts>pip --
version

140. Install PIP
If you do not have PIP installed, you can download and install it from this
page: https://pypi.org/project/pip/

141. Using a Package
Once the package is installed, it is ready to use.
Import the "camelcase" package into your project.
import camelcase
c = camelcase.CamelCase()
txt = "hello world"
print(c.hump(txt))

142. Exception Handling
The try block lets you test a block of code for errors.
The except block lets you handle the error.
The finally block lets you execute code, regardless of the result of the try- and except blocks.

143. try statement
When an error occurs, or exception as we call it, Python will normally stop and generate an error
message.
These exceptions can be handled using the try statement:
try:
print(x)
except:
print("An exception occurred")

144. Many Exceptions
You can define as many exception blocks as you want, e.g. if you want to execute a special block
of code for a special kind of error:
try:
print(x)
except NameError:
print("Variable x is not defined")
except:
print("Something else went wrong")

145. User Input
Python allows for user input.
That means we are able to ask the user for input.
The method is a bit different in Python 3.6 than Python 2.7.
Python 3.6 uses the input() method.
Python 2.7 uses the raw_input() method.

146. Example
username = input("Enter username:")
print("Username is: " + username)

147. File Handling
File handling is an important part of any web application.
Python has several functions for creating, reading, updating, and deleting files.
The key function for working with files in Python is the open() function.
The open() function takes two parameters; filename, and mode.
There are four different methods (modes) for opening a file:

148. There are four different methods (modes) for opening a file:
"r" - Read - Default value. Opens a file for reading, error if the file does not exist
"a" - Append - Opens a file for appending, creates the file if it does not exist
"w" - Write - Opens a file for writing, creates the file if it does not exist
"x" - Create - Creates the specified file, returns an error if the file exists

149. Syntax
f = open("demofile.txt")

150. Open a File on the Server
f = open("demofile.txt", "r")
print(f.read())

151. Write to an Existing File
To write to an existing file, you must add a parameter to the open() function:
"a" - Append - will append to the end of the file
"w" - Write - will overwrite any existing content

152. f = open("demofile2.txt", "a")
f.write("Now the file has more content!")
f.close()
#open and read the file after the appending:
f = open("demofile2.txt", "r")
print(f.read())

153. Create a New File
"x" - Create - will create a file, returns an error if the file exist
f = open("myfile.txt", "x")

154. Delete a File
To delete a file, you must import the OS module, and run its os.remove() function:
import os
os.remove("demofile.txt")