Exploring Docker

Problem Statement: Let say we have to setup multiple application (App 1, App 2 & App 3) on machine. All these application require different version of software/libraries dependencies. How we can setup applications so that there is no conflict of libraries version between applications.

Earlier times approach where we can setup different physical machines for all the applications. Following are some disadvantages:

Huge cost involved for setup different machines.
Wastage of resources in individual machines.
Difficult to scale & manage the applications.

Old Approach: Setup VMs (Virtual Machines) on top of one host machine & run applications separately. See below diagram

In this kind of hypervisor based virtualization model each VM has its own OS i.e. separate resources allocated for VM (RAM, HDD and CPU). Following are some disadvantages:

Entire OS loads first then the app start. So Boot time is slow.
VMs are generally huge is size (GB’s).
Wastage of unused resources in VM.
Deployment is not easy.

Latest Approach: Containerization – Process of packaging of an application with its required files, libraries/dependencies to run in efficient way in isolated user space called container.

Its a form of OS virtualization, where containers shares the host OS kernel. Containers are light weight as it holds only required files & libs & consume resources whenever required.

What is Docker?

‘Container based technology’ which enable developer to create, run & deploy application as efficient light weight container. You can create the containers using the docker images i.e. read only template. You can get the images for OS, Programming Language, Databases, DevOps etc.

Visit Docker Hub for more details.

Docker Installation:

Docker is easy to install application, available for variety of Linux, macOS & Windows. There are several methods to install the Docker on your machine, you can refer all the methods at docs.docker.com/

In this blog we will install docker using the shell script on Ubuntu box.

curl -fsSL https://get.docker.com -o get-docker.sh
sudo sh het-docker.sh

Checking the docker version after installation using docker -v or docker –version

Testing Docker Installation:

Docker is now installed on the system, lets run the first container to test the docker installation using docker official image “Hello-World”. You can refer the complete documentation of this image here.

Pulling the image of ‘hello-word‘ from docker hub. You can check all downloaded images in your local repository using docker images.

Now we have hello-world image present in local repository. We can use docker run command to launch the container using this image.

Listing all the container using docker ps -a command.

We are able to test the doker installation by running first container successfully. Let’s move to next step by creating the custom images by passing our own set of code.

Creating Custom Docker Image:

There are many options to create the custom docker image. Here we are going to use the Dockerfile to create multiple custom docker custom images.

Here I’m going to create two custom images using the base images of Python version 2.7 & 3.8 and will provide common python code for both the apps. Later going to create the containers for these images.

I have create one Dockerfile, first I’m using Python 2.7 version image as base.

Sample python script:

Creating custom image for python 2.7 using docker build command.

After this I have edited the Dockerfile & changed the Python version to 3.8

Creating second custom docker image for python 3.8:

Checking all the docker images: So we have our own custom images created. See below image python2.7app & python3.8app.

Launching Docker Containers:

Containers created for separate images & code is also executed.

Checking all the container using docker ps -a command

Check the details of containers like IP, Ports etc using inspect command.

Pushing custom images to Docker Hub:

First you have to sign up for docker hub: hub.docker. You will get you docker id i.e. username.

docker tag <image-id> username/<image-name>
docker login
# provide your docker hub credentials

To push the image :

docker push username/<image-id>

You can check your image in hub.docker

Removing the Docker Images/Containers:

# Remove all stopped containers 
docker rm $(docker ps -a -q)
# Remove single container 
docker rm <container-id>
# Remove single image
docker rmi <image-id>

Thanks!

Happy Learning! Your feedback would be appreciated!

Follow @shobhitsinghIN

ODI 12c – Setting CDC/Journalizing

In this blog we will see step by step how we can setup the change data capture (CDC)/journalizing in ODI 12c.

Change data capture as the name suggest the process to identify the change in source data whether the records inserted/updated or deleted from the source systems. After identifying the change data & applying the same in targets. We will explore here the complete process & objects required to setup the CDC in ODI 12c.

ODI Journalizing Modes:

Simple – Capture changes for individual data-stores in a model, does not support referential integrity between the data-store.

Consistent Set – It also support the referential integrity between data-stores. Group of datastores journalized in this mode is called ‘Consistent Set’.

Step 1. Import JKM:

Import the Journalizing Knowledge Model – JKM Oracle Simple

Create the Model for your source data-store. Select the ‘Journalizing Mode‘ as simple & select the correct JKM from drop down. Refer below screenshot.

Reverse engineer your tables, make sure it has some key.

Step 2. Add Subscriber:

Subscriber: It is a application or process which consume the captured change data. When subscribers have consumed the captured changes, later on changes were discarded from the journals.

If you do not want to add any subscriber to your data-store, by default ‘SUNOPSIS‘ will be there.

Step 3. Add to CDC:

You are adding your data-store to CDC process.

If you open your data-store, go to Journalizing tab. You will see a message that table is included in CDC. Also the clock sign will come on your data-store.

Step 4. Start Journal:

Start the journal, select the subscriber. Select context & run. It will create all the objects using which change data can be captured in J$ tables.

Below objects created in database. Two views are created: the JV$ view and the JV$D view.

TABLES: J$ACCOUNTS_STAGE & SNP_SUBSCRIBERS
TRIGGER – T$ACCOUNTS_STAGE
VIEWS: JV$ACCOUNTS_STAGE & JV$DACCOUNTS_STAGE

Subscriber Table:

ACCOUNTS_STAGE Table registered as subscriber in SNP_SUBSCRIBERS.

J$ Table:

I have inserted 4 records in my staging table ACCOUNTS_STAGE manually. After commit I have noticed that 4 records also inserted in my J$ Tabe i.e. J$ACCOUNTS_STAGE with consume flag as 0 i.e. records not yet consumed. J$ Table J$ACCOUNTS_STAGE has only 5 columns, last one is the key of table.

JRN_SUBSCRIBER
JRN_CONSUMED
JRN_FLAG
JRN_DATE
ACCOUNT_ID

Above records are inserted by the trigger T$ACCOUNTS_STAGE on ACCOUNTS_STAGE.

Step 5. Journalizing Filter in Mapping :

You can set your subscriber here in filter.

Step 6. Journalizing Data Only:

Tick the ‘Check box’ for ‘Journalizing Data Only‘.

JV$ view:

JV$ACCOUNTS_STAGE is used in the mappings where you select the option Journalized data only. This view is used to insert the records in I$ flow table.

Records from the J$ table ( J$ACCOUNTS_STAGE) are filtered using condition JRN_CONSUMED=1. If you have multiple records for 1 key, then it will pick the latest entry of the that key using JRN_DATE.

select	L.JRN_SUBSCRIBER AS  JRN_SUBSCRIBER,
L.ACCOUNT_ID AS  ACCOUNT_ID,
max(L.JRN_DATE) AS JRN_DATE
from DEV_SCHEMA.J$ACCOUNTS_STAGE L
where L.JRN_CONSUMED = '1'
group by L.JRN_SUBSCRIBER,L.ACCOUNT_ID

Locking of records in J$ table using below SQL update statements. When you start execution of mappings this is the first step.

update	DEV_SCHEMA.J$ACCOUNTS_STAGE
set	JRN_CONSUMED = '1'
where	(1=1)
AND JRN_SUBSCRIBER = 'SUNOPSIS'

JV$D View:

Data view is used to show the change data available for all subscribe in the J$ table without any consume filter, when you select the menu Journal Data from data-store.

I have inserted new 1 record & 1 updated in my staging table ACCOUNTS_STAGE manually. If you notice the JRN_FLAG is coming as I for update case also, code was present in trigger like that.

List of changed data if available: It is coming from JV$D view (JV$DACCOUNTS_STAGE)

At the end of mapping steps there is one step which cleans journalized table.

delete from J$ACCOUNTS_STAGE
where 	JRN_CONSUMED = '1'
AND JRN_SUBSCRIBER = 'SUNOPSIS' ;

Thanks!

Happy Learning! Your feedback would be appreciated!

Follow @shobhitsinghIN

Python [Post 07] | Tuple

A tuple is a collection which is ordered and unchangeable. It is similar to list, but a tuple is immutable unlike lists which are mutable.

It is created by placing items inside a parentheses (), separated by comma. Parentheses is optional.

# Creating Tuple

empty_tuple = ()
my_tup1 = 'N','S','E','W'
my_tup2 = ('North','South','East','West')

print(type(empty_tuple))
print(my_tup1)
print(my_tup2)

<class ‘tuple’>
(‘N’, ‘S’, ‘E’, ‘W’)
(‘North’, ‘South’, ‘East’, ‘West’)

Other way to create tuple by using the tuple() constructor. See below example.

my_tup3 = tuple((1,'South',5.5,('A','B','C'),[0,1,2]))

print(my_tup3)
print(type(my_tup3))

(1, ‘South’, 5.5, (‘A’, ‘B’, ‘C’), [0, 1, 2])
<class ‘tuple’>

# Creating a tuple having single value

my_tup4 = (4)
print(type(my_tup4)) # But the result is showing int, i.e. this is not a tuple

To create a tuple having single value, Just include comma at last.

my_tup4 = (4,)
print(type(my_tup4)) # Now its a tuple

Some Built-in Python Functions

my_tup5 = 1,2.5,3,4

print(type(my_tup5)) # Type
print(len(my_tup5)) # len Function - Gives the total length of the tuple.
print(max(my_tup5)) # max Function - Returns element from the tuple with maximum value.
print(min(my_tup5)) # min Function - Returns element from the tuple with minimum value.

<class ‘tuple’>
4
4
1

### Accessing Tuple Values – Indexing & Slicing

Use the index operator [] to access an item in a tuple. We can use a : to perform slicing which extracts chunk of more than one element as per input. In slicing last index is not included.

sides = 'East','West','North','South'

# Fetch the first element of list sides

print(sides[0])

East

# Fetch the last element of list sides

print(sides[-1])

South

# fetch elements start from index 1st till last

print(sides[1:])

(‘West’, ‘North’, ‘South’)

# fetch elements upto 2nd index, but 2nd is not included

print(sides [:2])

(‘East’, ‘West’)

# fetch element from 1st index to 3rd index

print(sides [1:3])

(‘West’, ‘North’)

# fetching values in case of nested tuple

my_tup = tuple((1,'South',5.5,('A','B','C'),[0,1,2]))

print(my_tup[3][0])
print(my_tup[3][2])

A
C

### Updating Tuples

Python Tuple is immutable i.e. the elements inside a tuple cannot be changed!

sides = ('East','West','North','South')

# Let's try to change the elements of lists sides

sides[0]= 1

TypeError Traceback (most recent call last)
<ipython-input-14-b1dd30231e62> in <module>()
3 # Let’s try to change the elements of lists sides
4
—-> 5 sides[0]= 1
TypeError: ‘tuple’ object does not support item assignment

### Deleting Tuples

Individual element in tuple cannot be removed. Entire tuple can be removed by using del statement.

# Removing tuple completely

del sides

sides # This will raise exception, as sides tuple removed

NameError Traceback (most recent call last)
<ipython-input-16-7623a01b7793> in <module>()
—-> 1 sides # This will raise exception, as sides tuple removed
NameError: name ‘sides’ is not defined

### Concatenation & Repetition of Tuples

sides = ('East','West','North','South')
modesides = ('North-East','North-East','South-East','South-West')

print(sides)
print(modesides)

(‘East’, ‘West’, ‘North’, ‘South’)
(‘North-East’, ‘North-East’, ‘South-East’, ‘South-West’)

# Concatenation

sides = sides + modesides
print(sides)

(‘East’, ‘West’, ‘North’, ‘South’, ‘North-East’, ‘North-East’, ‘South-East’, ‘South-West’)

# Repetition

sides = sides * 2
print(sides)

(‘East’, ‘West’, ‘North’, ‘South’, ‘North-East’, ‘North-East’, ‘South-East’, ‘South-West’, ‘East’, ‘West’, ‘North’, ‘South’, ‘North-East’, ‘North-East’, ‘South-East’, ‘South-West’)

### Tuple Method

Python includes following tuple methods.

Index() :

Returns the index of the first matched item.

sides = 'EAST','West','North','East','South','East'

print(sides.index('East'))
print(sides.index('West'))

3
1

Count():

Returns the count of number of items passed as an argument.

print(sides.count('East'))

Thanks!

Happy Learning! Your feedback would be appreciated!

shobhitsingh.in
Github Code Link

Follow @shobhitsinghIN

Python [Post 06] | Dictionary

Python dictionary is an un-ordered collection of items. It consists of a key value pairs.

Python dictionary is un-ordered & cannot be sorted.
Value can be almost any Python object.
Value can be accessed by unique key in the dictionary.
Keys must be of an immutable data type. Example – strings, numbers or tuples.

Creating a dictionary is as simple as placing items inside curly braces {} separated by comma. An item has a key and the corresponding value expressed as a pair, key: value.

{‘key1′:’value1′,’key2′:’value2’}

# Examples of Python Dictionary:

# Dictionary having string keys & string value
my_dict0 = { "N": "North", "S": "South", "E": "East", "W": "West" }

# Dictionary having integer keys & string value
my_dict1 = { 1: 'North', 2: 'South', 3: 'East', 4: 'West'}

# Dictionary having string keys & integer value
my_dict2 = { 'North' : 1, 'South': 2, 'East': 3,'West':4}

# Dictionary having mixed keys & values
my_dict3 = { 'N' : 'North', 2: 'South', 'East': 3,'West':'W', "ComplexNumber":5+500j, 5.5:[1,2,3,4]}

# Nested Dictionary
my_dict4 = { 'Aphabets' : { 'A':{'Fruit':'Apple','Object':'Aeroplane'},'B':{'Fruit':'Banana','Object':'Ball'}} ,
'Numbers' : { 0: 'Zero', 1:'One', 2:'Two', 3:'Three', 4:'Four', 5:'Five', 6:'Six', 7:'Seven'}
}
print(my_dict0)
print(my_dict1)
print(my_dict2)
print(my_dict3)
print(my_dict4)

{‘N’: ‘North’, ‘S’: ‘South’, ‘E’: ‘East’, ‘W’: ‘West’}
{1: ‘North’, 2: ‘South’, 3: ‘East’, 4: ‘West’}
{‘North’: 1, ‘South’: 2, ‘East’: 3, ‘West’: 4}
{‘N’: ‘North’, 2: ‘South’, ‘East’: 3, ‘West’: ‘W’, ‘ComplexNumber’: (5+500j), 5.5: [1, 2, 3, 4]}
{‘Aphabets’: {‘A’: {‘Fruit’: ‘Apple’, ‘Object’: ‘Aeroplane’}, ‘B’: {‘Fruit’: ‘Banana’, ‘Object’: ‘Ball’}}, ‘Numbers’: {0: ‘Zero’, 1: ‘One’, 2: ‘Two’, 3: ‘Three’, 4: ‘Four’, 5: ‘Five’, 6: ‘Six’, 7: ‘Seven’}}

Other way to create dictionary to use the dict() constructor to make a dictionary:

sides = dict(N="North", S="South", E="East",W="West")
print(sides)

{‘N’: ‘North’, ‘S’: ‘South’, ‘E’: ‘East’, ‘W’: ‘West’}

Access elements from a dictionary

# Fetching dictionary values by key

print(sides['N'])
print(sides.get('S'))

North
South

# Nested Dictionary
my_dict = { 'Aphabets' : { 'A':{'Fruit':'Apple','Object':'Aeroplane'},'B':{'Fruit':'Banana','Object':'Ball'}} ,
'Numbers' : { 0: 'Zero', 1:'One', 2:'Two', 3:'Three', 4:'Four', 5:'Five', 6:'Six', 7:'Seven'}
}

smy_dict['Aphabets']['A']['Object']

‘Aeroplane’

my_dict4['Numbers'][5]

‘Five’

In Python dictionary no duplicate key is allowed.

# Creating a dictionary having duplicate keys

sides ={ "N": "East", "S": "South", "N": "West", "N": "North" }
print(sides)

{‘N’: ‘North’, ‘S’: ‘South’}

When duplicate keys found during dictionary creation, the last assignment is final one. See above example.

### Updating Dictionary

Adding a new key-value pair, modifying an existing key-value pair, or deleting an existing key-value pair.

# Creating a new dictionary

sides = dict(N="North", S="South", E="East",W="West")
print(sides)

{‘N’: ‘North’, ‘S’: ‘South’, ‘E’: ‘East’, ‘W’: ‘West’}

Adding a new key:value pairs to existing dictionary

sides['NE'] = 'North-East'
sides['NW'] = 'North-West'
print(sides)

{‘N’: ‘North’, ‘S’: ‘South’, ‘E’: ‘East’, ‘W’: ‘West’, ‘NE’: ‘North-East’, ‘NW’: ‘North-West’}

Updating key:value pair

sides['NE'] = 'North East'
sides['NW'] = 'North West'
print(sides)

{‘N’: ‘North’, ‘S’: ‘South’, ‘E’: ‘East’, ‘W’: ‘West’, ‘NE’: ‘North East’, ‘NW’: ‘North West’}

sides['NE']

‘North East’

Deleting an existing key:value pair

print(sides)

{‘N’: ‘North’, ‘S’: ‘South’, ‘E’: ‘East’, ‘W’: ‘West’, ‘NE’: ‘North East’, ‘NW’: ‘North West’}

del sides ['N'] # Remove the provided Key
print(sides)

{‘S’: ‘South’, ‘E’: ‘East’, ‘W’: ‘West’, ‘NE’: ‘North East’, ‘NW’: ‘North West’}

del sides ; # delete dictionary completely

### Dictionary Methods

Python Dictionary provides so many methods. See below some examples

sides = dict(N="North", S="South", E="East",W="West")
print(sides)

{‘N’: ‘North’, ‘S’: ‘South’, ‘E’: ‘East’, ‘W’: ‘West’}

Get()

It return Value for Key.

print(sides.get('S'))

South

Items(), Keys () & Value()

Item – It return the list with all dictionary keys with values.
Keys – It return list of dictionary dict’s keys.
Value – It returns list of dictionary dict’s values.

print(sides.items())
print(sides.keys())
print(sides.values())

dict_items([(‘N’, ‘North’), (‘S’, ‘South’), (‘E’, ‘East’), (‘W’, ‘West’)])
dict_keys([‘N’, ‘S’, ‘E’, ‘W’])
dict_values([‘North’, ‘South’, ‘East’, ‘West’])

Copy()

It creates the copy of the dictionary into other dictionary.

new_sides = {}
new_sides = sides.copy()

print(new_sides)

{‘N’: ‘North’, ‘S’: ‘South’, ‘E’: ‘East’, ‘W’: ‘West’}

Update()

Adds dictionary key-values pairs to another dictionary.

sides = dict(N="North", S="South", E="East",W="West")
some_more_sides = dict(NE="North-East", SE="South-East")

print(sides)
print(some_more_sides)

{‘N’: ‘North’, ‘S’: ‘South’, ‘E’: ‘East’, ‘W’: ‘West’}
{‘NE’: ‘North-East’, ‘SE’: ‘South-East’}

sides.update(some_more_sides)
print(sides)

{‘N’: ‘North’, ‘S’: ‘South’, ‘E’: ‘East’, ‘W’: ‘West’, ‘NE’: ‘North-East’, ‘SE’: ‘South-East’}

Clear()

Removes all elements of dictionary.

some_more_sides.clear(); # Remove all entries in dictionary
print(some_more_sides)

{}

Thanks!

Happy Learning! Your feedback would be appreciated!

shobhitsingh.in

Github Code Link

Follow @shobhitsinghIN

Python [Post 05] | Lists

A list in Python is an ordered group of items. Items in a list need not be of the same type. A list is created by placing all the items inside a square bracket, separated by commas.

# Lists Examples

my_empty_list = []
number_list = [1,2,3,4,5]
str_list = ['A','B','C','D','Hello Python']
mix_list = ['A',1,'B',2,'C',12.5,5+500j]
nested_list = ['A',1,'B',2,['X','Y','Z']]

print(number_list)
print(str_list)
print(mix_list)
print(nested_list)

[1, 2, 3, 4, 5]
[‘A’, ‘B’, ‘C’, ‘D’, ‘Hello Python’]
[‘A’, 1, ‘B’, 2, ‘C’, 12.5, (5+500j)]
[‘A’, 1, ‘B’, 2, [‘X’, ‘Y’, ‘Z’]]

Some Built-in Python Functions

my_list = [1,2.5,3,4.6,5,6]

print(len(my_list)) # len Function - Gives the total length of the list.
print(max(my_list)) # max Function - Returns element from the list with maximum value.
print(min(my_list)) # min Function - Returns element from the list with minimum value.

6
6
1

### List Indexing & Slicing

Use the index operator [] to access an item in a list. We can use a : to perform slicing which extracts chunk of more than one element as per input. In slicing last index is not included.

sides = ['East','West','North','South']

# Fetch the first element of list sides

sides[0]

‘East’

# Fetch the last element of list sides

sides[-1]

‘South’

# fetch elements start from index 1st till last

sides[1:]

[‘West’, ‘North’, ‘South’]

# fetch elements upto 2nd index, but 2nd is not included

sides [:2]

[‘East’, ‘West’]

# fetch element from 1st index to 3rd index

sides [1:3]

[‘West’, ‘North’]

Unlike Python Strings, Python Lists are mutable i.e. the elements inside a list can be changed!

sides = ['East','West','North','South']
print(sides)

# Let's try to change the elements of lists sides

sides[0]= 3.0
sides[1]='Hello World'
sides[2]='Python World'
sides[3]= 12345

print(sides)

[‘East’, ‘West’, ‘North’, ‘South’]
[3.0, ‘Hello World’, ‘Python World’, 12345]

Nested Lists

A list inside a list.

some_sides = ['East','West','North','South']
more_sides1 = ['North-East','North-West']
more_sides2 = ['South-East','Soth-West']

nested_sides = [some_sides,more_sides1,more_sides2]

print(nested_sides)

[[‘East’, ‘West’, ‘North’, ‘South’], [‘North-East’, ‘North-West’], [‘South-East’, ‘Soth-West’]]

# Fetch the first element of first list

print(nested_sides[0])
print(nested_sides[0][0])

[‘East’, ‘West’, ‘North’, ‘South’]
East

# Fetch the second element of third list

print(nested_sides[2])
print(nested_sides[2][1])

[‘South-East’, ‘Soth-West’]
Soth-West

### Lists Methods

Python includes following list methods

# Creating a new list

sides = ['East','West','North','South']

Append():

Adds single element to the end of a list. Length of the list increases by 1 index.

# Example 1: Append Element in list

sides.append('North-East')
print(sides)

[‘East’, ‘West’, ‘North’, ‘South’, ‘North-East’]

# Other way to append

sides = sides + ['South-East','South-West']
print(sides)

[‘East’, ‘West’, ‘North’, ‘South’, ‘North-East’, ‘South-East’, ‘South-West’]

# Example 2: Append List with List (This will create nested list)

sides = ['East','West']
more_sides = ['North','South','North-East']

sides.append(more_sides)
print(sides)

[‘East’, ‘West’, [‘North’, ‘South’, ‘North-East’]]

Extend():

Add all elements of a list to the another list. It will not create nested list.

# Example - Extending Lists

sides = ['East','West']
more_sides = ['North','South','North-East']

sides.extend(more_sides)
print(sides)

[‘East’, ‘West’, ‘North’, ‘South’, ‘North-East’]

Insert():

Inserts an element at the position mentioned in its arguments. It takes two arguments, position and element.

# Example Insert

sides = ['West','North']

print(sides)

sides.insert(2,'South')
sides.insert(3,'South-East')
sides.insert(0,'East')

print(sides)

[‘West’, ‘North’]
[‘East’, ‘West’, ‘North’, ‘South’, ‘South-East’]

Pop():

Removes and returns an element at the given index. By default pop takes off the last index, but you can also specify which index to pop off.

sides.pop() # Pop off the last indexed item, by default

‘South-East’

print(sides)

[‘East’, ‘West’, ‘North’, ‘South’]

sides.pop(3) # Pop off the 3rd indexed item

‘South’

print(sides)

[‘East’, ‘West’, ‘North’]

Remove():

It is used to delete the first occurrence of item mentioned in its arguments.

sides = ['East','West','North','East','South']

sides.remove('East')
print(sides)

[‘West’, ‘North’, ‘East’, ‘South’]

Clear():

Removes all elements from the list.

sides = ['East','West','North','South']
print(sides)

[‘East’, ‘West’, ‘North’, ‘South’]

sides.clear() # Clear the list

print(len(sides))
print(sides)

0
[]

Index() :

Returns the index of the first matched item.

sides = ['EAST','West','North','East','South','East']

sides.index('East')

Count():

Returns the count of number of items passed as an argument.

sides.count('East')

Sort():

Sort items in a list in ascending order.

sides = ['West','North','East','South']

print(sides)
sides.sort()
print(sides)

[‘West’, ‘North’, ‘East’, ‘South’]
[‘East’, ‘North’, ‘South’, ‘West’]

Reverse():

Reverse the order of items in the list.

print(sides)
sides.reverse()
print(sides)

[‘East’, ‘North’, ‘South’, ‘West’]
[‘West’, ‘South’, ‘North’, ‘East’]

Thanks!

Happy Learning! Your feedback would be appreciated!

shobhitsingh.in

Github Code

Follow @shobhitsinghIN

Python [Post 04] | Strings

Folks,

In this blog post we will explore Python strings & string methods. Python strings are sequences of characters. Here are some examples of strings.

# Printing String

print('This is a string!') # Enclosed using single quote

print("This is also a string!") # Enclosed using double quote

print("""This is also a string,
also having next line.""") # Enclosed using triple quote. Multiple lines are generally put in triple quotes.

print("It's ok!") # Use double quote to enclose the string, if string is having single quote
print('P') # Python treat this single character also as string

This is a string!
This is also a string!
This is also a string,
also having next line.
It’s ok!
P

### String Indexing

Python strings are sequences of individual characters. We can access characters in strings by index. In Python index starts from 0, also if you want to start from the end, instead of the beginning then use a negative index.

Indexing Example: String x = ‘Python’

+ve Index 0 1 2 3 4 5
+ve Index 0 -5 -4 -3 -2 -1

# String Variable
x = 'Python'

x[0] # Fetch the first character of string x

‘P’

x[1] # Fetch the second character of string x

‘y’

x[-1] # Fetch the last character of string x

‘n’

Python strings are immutable. i.e. Once string is created, the elements within it can not be changed or replaced.

# Let's try to change the first letter to 'J' of string x
x[0] = 'J'

TypeError Traceback (most recent call last)

<ipython-input-6-5b400f918714> in <module>()
1 # Let’s try to change the first letter to ‘J’ of string x
—-> 2 x[0] = ‘J’

TypeError: ‘str’ object does not support item assignment

You can “update” an existing string by (re)assigning a variable to another string.

x = 'J' + x[1:]
print(x)

Jython

### Slicing Python String

We can use a : to perform slicing which extracts chunk of more than one character as per input. In slicing last index is not included.

String x = ‘Python’

+ve Index 0 1 2 3 4 5

+ve Index 0 -5 -4 -3 -2 -1

For Example:

# String Variable
x = 'Python'

x[0:2] # fetch the first 2 character of string x. x[0:2] is same as x[:2]

‘Py’

x[:3] # fetch the first 3 character of string x

‘Pyt’

x[2:5] # fetch character from 2nd index to 3rd index

‘tho’

x[2:] # fetch charcters start from index 2nd till last

‘thon’

x[:3] # fetch charcters upto 3rd index, but 3rd is not included

‘Pyt’

x[-5:-1] # Negative Index also works in slicing

‘ytho’

x[::] # fetch complete string

‘Python’

Skipping Characters using third parameter

x = 'Python'
x[::1] # Default is 1

‘Python’

x[::2] # Skip every 2nd character

‘Pto’

x[0:5:2] # Skip every 2nd character

‘Pto’

x[::-1] # Reverse String

‘nohtyP’

### String Methods Examples

Python String provides so many methods to do the string manipulations. See below examples.

# Split - Splits string as per provided delimiter ( default space) and returns list of substrings;

x = 'Python is fully-functional programming language that can do almost anything'
print(x.split())

[‘Python’, ‘is’, ‘fully-functional’, ‘programming’, ‘language’, ‘that’, ‘can’, ‘do’, ‘almost’, ‘anything’]

x = 'A,B,C,D,E,F'
print(x.split(',')) # Comma as delimeter

[‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘F’]

# Upper & Lower Case

x = 'Python'
print(x.upper())
print(x.lower())

PYTHON
python

# Checking String whether contains only alpha or numeric

x = 'Python3'
print(x.isalnum())
print(x.isalpha())
print(x.isnumeric())
len(x)

True
False
False
7

Lstrip, RStrip & Strip Method – For removing white spaces

# lstrip - Remove white space from left

x = ' Python3 '
x.lstrip()

‘Python3 ‘

# rstrip - Remove white space from left

x = ' Python3 '
x.rstrip()

‘ Python3’

# rstrip - Remove white space from left & right

x = ' Python3 '
x.strip()

‘Python3’

.format() String Method

Insert objects dynamically in the string using assigment keywords or index. It can also persorm alignment, padding & precision of floating point numbers.

import datetime
d = str(datetime.datetime.now())

# Example 1 -

x = "Today's date & time is {}"

x.format(d)

“Today’s date & time is 2018-07-08 02:04:47.893499”

# Example 2

x = "Today's date & time is %s" %datetime.datetime.now()

print(x)

Today’s date & time is 2018-07-08 02:04:49.885035

# Example 3

print('a {f} in need is a {f} indeed'.format(f='friend'))
print('a {0} in need is a {0} indeed'.format('friend'))

a friend in need is a friend indeed
a friend in need is a friend indeed

# String Formatting Operator - %
# Oldest method involves placeholders using the modulo % character. %s for string, %c is for character, %i integer, %f float etc

print('a %s in need is a %s indeed' %('friend','friend'))

x = "Today's date & time is %s" %datetime.datetime.now()
print(x)

x = "My name is %s, my age is %i & my height is %f" % ('John', 21, 150.56)
print(x)

a friend in need is a friend indeed
Today’s date & time is 2018-07-08 02:04:50.634701
My name is John, my age is 21 & my height is 150.560000

Precision of Float with .format() Method

You can add precision for float point numbers in string. See below example.

x = “My height is %5.1f” % (150.5678)

.1f stands for how many numbers to show past the decimal point.
5 would be the minimum number of characters the string should contain. Padded with whitespace if the entire number does not have this many digits.

x = "My height is %5.1f" % (150.5678)
print(x)

My height is 150.6

x = "My height is %15.2f" % (150.5678)
print(x)

My height is 150.57

Padding & Alignment with .format() Method

# Padding

print('{0:5} | {1:3}'.format('FName', 'Age'))
print('{0:5} | {1:3}'.format('A', 14))
print('{0:5} | {1:3}'.format('B', 12))

FName | Age
A | 14
B | 12

By default, .format() aligns text to the left, numbers to the right.
Pass an optional <,^, or > to set a left, center or right alignment as per requirement.

# Alignment

print('{0:^5} | {1:^3}'.format('FName', 'Age'))
print('{0:^5} | {1:^3}'.format('A', 14))
print('{0:^5} | {1:^3}'.format('B', 12))

FName | Age
A | 14
B | 12

print('{0:-^10} | {1:-^10}'.format('FName', 'Age'))

–FName— | —Age—-

There are many more string methods eg. count, find, decode, encode, index etc.

Thanks!

Happy Learning! Your feedback would be appreciated!
shobhitsingh.in

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Python [Post 03] | Numbers

Folks,
In this blog we will explore different Python numeric types, arithmetic operations, mathematical fuctions, variable assignment & number conversion.

For Python Overview & Basic – Refer this Blog Post

Python has mainly three diffrent of numeric types.

int
float
complex

Integers (int)

Int/Integer, is basically a whole number (+ve or -ve), without decimals & of unlimited length.

Example of Integers: -5, 500, 20001543646546231654646465465454544545454554

# Integer Example 1
print(-5)
type(5)

-5
int

# Integer Example 2
print(500)
type(500)

500
int

# Integer Example 3
print(20001543646546231654646465465454544545454554)
type(20001543646546231654646465465454544545454554)

20001543646546231654646465465454544545454554
int

Float

Floating point numbers is a number, (+ve or -ve), represent real numbers and they have a decimal points in them, or use an exponential (e) to define the number.

Exampe of Floats: -5.5 , 500.5, 5E2

5E2 (5 times 10 to the power of 2) is also an example of a floating point number in Python.

# Float Example 1
print(-5.5)
type(-5.5)

-5.5
float

# Float Example 2
print(500.5)
type(500.5)

500.5
float

# Float Example 3
print(5E2)
type(5E2)

500.0
float

Complex Number

Numbers in the form of (a + bj), where a and b are floats and j represents the square root of -1. Real part of the number is a, and the imaginary part is b.

Exampe of Complex Number: 5+500j

# Complex Example 1
5+500j

(5+500j)

type(5+500j)

complex

Artithmetic Operations

# Additon of numbers
5+5

# Substraction of numbers
10-5

# Multiplication of numbers
10*5

# Division of nuumbers
10/5

2.0

# Floor Divison (// operator truncates the decimal without rounding)
10//4

# Exponent
5**2

# Modulus (% operator returns the remainder after division)
5%2

Mathematical Fuctions

Python also have some functions that perform mathematical calculations

# importing "math" for mathematical operations
import math

# Ceil Function
print (math.ceil(5.6))

# Floor Function
print (math.floor(5.6))

# Exponential Function
print (math.exp(5))

148.4131591025766

# Square Root Function
print (math.sqrt(16))

4.0

# Factorial Function
print (math.factorial(5))

120

# Absolute Function - Positive Number
print(abs(-5))

# Round Function - Number rounded to n digits from the decimal point
print(round(5.56))

# Round Function with 2nd argument for how many digits to round
print(round(5.56,1))

6
5.6

# Minimun Function - Finds smallest of its arguments
print (min(5,10,2,22))

# Mamimun Function - Finds largest of its arguments
print (min(5,10,2,22))

Variable Assignemnt

# Create an object/Variable called "length" and assign it the number 50
length = 50
print(length)

# Reassignment - Overrites value
length = 10
print(length)

length = 10
width = 5.6
height = 10.6

print(length * width * height)

593.6

Numerical Type Conversion

# Example 1:
height = 10.6
type(height)

float

# Let's convert this variable into int
height= int(height)
print(height)
type(height)

10
int

# Example 1:
length = 10
type(length)

int

# Let's convert this variable into foat
length= float(length)
print(length)
type(length)

10.0
float

Thanks!

Happy Learning! Your feedback would be appreciated!

shobhitsingh.in
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Python [Post 02] | Variables

In Python a variable is created when we assign value to it. It does not required any explicit declaration. Use the assignment operator = to assign the value to a variable.

Variable Names Rules

Must start with a letter or the underscore character. Cannot start with a number.
Can only contain alpha-numeric characters and underscores (A-z, 0-9, & _ ).
Variable names are case-sensitive.
Avoid using Python Built-keywords. Like str, type, list etc.

#Example:

name = "John" # String Variable Assignment
age = 50 # Integer Variable Assignment
height = 150.50 # Float Variable Assignment

Using Python’s built-in function type() you can check what type of object is assigned to a variable.

Here are the list of Python data type:

int
float
str
list
tuple
dict
set
bool

# Exapmple

type(name)

str

## Dynamic Typing

In Python you can reassign variables to different data types. Python is very flexible in assigning data types.

# Example, Here Integer Assignment

x=50

type(x)

int

x="Hello, World!" # Re-assigned X Now String Assignment

type(x)

str

x=12.20+4j # Re-assigned X Now String Assignment

type(x)

complex

x=(1,2,3,4,5) # Re-assigned X Now Tuple Assignment

type(x)

tuple

## Re-assigning Variables

Python allow you to reassign variables with a reference to the same object.

a=50
print(a)

a = a + a
print(a)

100

a += 50
print(a)

150

a -= 10
print(a)

140

a *= 2
print(a)

280

a /= 5
print(a)

56.0

# Multiple Assignment

Python allows you to assign a value to multiple variables simultaneously.

# Example 1

length = width = height = 50

print (length)
print (width)
print (height)

50
50
50

# Example 2

length, width, height = (10,50,60)

print (length)
print (width)
print (height)

10
50
60

Thanks!

Happy Learning! Your feedback would be appreciated!

shobhitsingh.in

GitHub Code

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Python [Post 01] | Overview & Basics

What is Python?

Python is a general purpose object-oriented programming language with high-level programming capabilities. Developed by Guido van Rossum in the late eighties and early nineties at the National Research Institute for Mathematics and Computer Science in the Netherlands.

Open Source general-purpose programming language.
High-level programming language (i.e. independent of the computer’s hardware).
Interpreted (i.e. not need to compile your program before executing it, Python is processed at run-time by the interpreter)
Multiple Programming Paradigms ( i.e. Python supports object oriented programming, imperative and functional programming or procedural styles)
Code Readability – Python is easy to read, write & maintain.
Interactive – IDLE is Python’s built-in Integrated Development Environment. It has a Python shell window, which gives you access to the Python interactive mode.

Python is fully-functional programming language that can do almost anything.

You can install latest Python from this website – https://www.python.org/

Please see below YouTube video for Python Installation on you Windows Machine in 2 minutes.

After installation you can check the Python Version using Command Prompt.

Hello, World! in Python programming.

print("Hello World!")

Thanks!

Happy Learning! Your feedback would be appreciated!
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How to send email using Python.

Folks,

In this blog we will explore how send email to single/multiple email id using python Script.

Python Script: See detailed comments in the Python Script.


# import the smtplib module.
import smtplib

# from user details
from_user_email_id =  [provide_your_email_id_here]
from_user_email_pwd = [provide_your_email_id_password]

# Email Subject
email_subject = [provide_your_email_subject]

# To user email ids
to_user_email_id = [provide_list_of_to_email_ids_comma_seperated]

# set up the SMTP server
s = smtplib.SMTP(host=[provide_smtp_host_address_here], port=[provide_smtp_port_here]])
s.ehlo()
s.starttls()
s.ehlo

# login the SMTP server using from email id and password.
s.login(from_user_email_id, from_user_email_pwd)

# Preparing email message header and body.
email_header = 'To:' + ", ".join(to_user_email_id)  + '\n' + 'From: ' + from_user_email_id + '\n' + 'Subject: ' +  email_subject + '  \n'
email_body = email_header + [provide_here_email_text]

# sending email
s.sendmail(from_user_email_id, to_user_email_id, email_body)

s.close()

After providing all the required information & save your file in .py extension. Refer below example.

Execute Script:

Result:

Thanks!

Happy Learning! Your feedback would be appreciated!