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Regular Expression in Python Part III: Learn To Substitute With Re

Posted on September 16, 2020September 16, 2020 by Dexlab

This is the 3rd part of the ongoing Regex or, regular expression in Python series where we are discussing how to handle textual data. In the second part we introduced you to the re library and in this third segment, we are going to be discussing how to substitute characters or, words with re library.

Re library has a wide range of methods to deal with textual data, one such method is .sub() which helps us substitute alphabets or words based on the patterns we build. This method can be used with .match() method and .search() method, both having differences in the way they extract a pattern.

Difference between .match() & .search()

.match() :- This method extracts the required text only at the begging.

.search() :-This can extract the required string from the entire text but only at the first occurrence

In the above code you can see that even though the word “Hello” is in the middle of the text we are able to fetch it because of the special attribute of the .search() method. Here we are again using “Hello dexlab…!” as an example and .compile() is being used to create and apply our pattern.

Now suppose if we want to substitute the word “Hello” with another string “Hi” we will have to use .sub() method from the re library. But there are ways to use this method directly or indirectly.

First let’s see the direct method.

In the above line of code we first mention what we want to substitute and with what and then we add the text.

Second way to do this is by first using .compile() method to build the pattern and then use that pattern to substitute the alphabet or word.

The above pattern in the .complie() method states that there is a word with the first alphabet in uppercase combined with lowercase alphabets to be substituted with the word “Hi”. This pattern can match any string with the same characteristics, for example:-

Look at the text used in the .sub() method, now instead of “Hello” we have “Pello” with the same characteristics substituted with the word “Hi”. But one must not forget this pattern can also be used in the .sub() method directly and the use of .compile() method is optional. .compile() method is used only to create an object based code.

So, this wraps up the discussion on how to substitute characters or, words with re library. Hopefully, you found this blog informative, if you wish to find more Python Certification course topics, keep following the Dexlab Analytics blog.

Regular Expression in Python Part II: Using re library for textual data

Posted on September 15, 2020September 15, 2020 by Dexlab

This is the second part of the Regex series, where we will be continuing on by introducing you to another library in python, the re library. The previous blog introduced you to the Regex library in Python, and you learned about meta-characters and literals which could be used for creating patterns. This particular segment is about introducing the re library to help you with textual data analysis.

Re library in python holds the key to deal with all the problems relating to textual data analysis. This library provides a range of methods that can help you build patterns and extract or substitute the desired string. For example, suppose you want to change all the negative words to positive in a novel, for that all you need to have is a soft copy of the same and then you can import the re library and use its predefined methods first to make a pattern to extract the words and then substitute it to make the required changes.

Here one such method which we are going to use today from the re library is .compile() combined with .match() method to build and extract the pattern with the help of literals and meta-characters explained in the previous blog.

.compile() and .match() Methods

.complie() is used to build the pattern. You can use the meta-characters and literals within the parenthesis to build the pattern of the word which you want to extract or change. This is practically the first step without which not much can be done in re library. But why do we need a pattern and what is it that makes it necessary? To answer this question I am going to use few steps:-

First thing to do is to observe the word or the string and see what is it that makes that specific word or words which you want to extract different from the rest of the text i.e. is the word a combination of digit or alphabet or special character, is there a special character before and after the word etc.
Now recall all the meta-characters we have studied so far.
Combine them with the .complie() method which basically helps us bring the meta-characters together.
Now all there is left for us to do is apply the pattern on the text.

Therefore knowledge of meta-characters is necessary to form patterns to manipulate your textual data.

Now let’s see how to import re library and practically solve few of the Regex questions.

Use the above code to import the Regex library.

Question 1: How to make a pattern to extract the entire string “Hello dexlab…!!”?

In the above code we are using a combination of. (period)and * where

. (period) means match alpha-numeric or special character
* means match anything zero or more times

When combined together this means that you can match alpha-numeric or special characters zero or more times. Therefore the end result is:-

.match()method has a special property that it can match anything only at the beginning of the line. Suppose I want to extract “Hello” from a string, .match()method will only work when word is at the 0 index.

Question: How to extract and match only special characters?

The above code is matching only the space which is at the 0^th index but not all the simultaneous special characters. To make a pattern that can match all the special characters we can use *

You can try ? and + to check the difference it makes on the output.

Question: How to extract numbers and special characters?

Now you must be wondering why the above code did not recognize the special characters after the numbers like @ and space. Here you must remember that the output you get is based on the pattern you make. In the above code we mentioned nothing that matches anything after the numbers. So we further need to expand our line of codes.

Question: How to extract only the output?

You can use the slice operator [] to extract only the text by using 0 index.

You must have picked up the fundamentals of the re library from the blog, watch the video attached below to follow the tutorial step by step. Follow the Regex series to gain expertise in textual data handling. Dexlab Analytics blog has more interesting and informative posts on Python Programming training.

Regular Expression in Python Part I: Introducing Regex Library

Posted on September 14, 2020September 14, 2020 by Dexlab

Python is a versatile programming language and it has a rich library. In the visualization series we introduced you to different libraries used for data visualization purposes. Now, we introduce you to the Regex library in Python for handling textual data.

In Python to perform pattern recognition on textual data Regex is a library that provides a range of methods which when used with right pattern gives us the desired results. For example, if you want to change the spelling of colour to color in your text you can easily do so with the help of a given method provided that you form the pattern correctly.

Type of textual data in Regex

Literals:- In Python literals are the characters or words with their original meaning intact like the word dog means a literal dog and there is no hidden meaning behind that word.

Meta-characters:- These are the words or characters which hold special meaning for example \n means a new line or \t means tab separated values.

Given below are few of the meta-characters used in python with their meanings:-

\d – Matches a digit .i.e. \d= 1 ,\d\d= 23, \d\d\d = 345

\w – Matches alpha-numeric characters i.e. \w= 1, \w= a, \w\w= a1

\W– Matches special characters i.e. \W= %

Dog[ogn]– Matches a single character within the square bracketsi.e. Dogo, Dogg, Dogn

Dog(ogn) – Matches the entire string within the parenthesisi.e. Dogogn

Dog(ogn|aaa)– Matches either ogn or aaa i.e. Dogogn or Dogaaa

*– Matches 0 or more characters i.e. tre* = tree, tre*= tr, tre*= treeeeee

?– Matches 0 or 1 character i.e. colou?r= color, colou?r= colour

+ – Matches 1 or more character i.e. tre+= tree, tre+= treee, tre+≠tre

. – Matches alpha-numeric or special characters but only one time i.e. tre.= tree, tre.= tre#, tre.=tre1, tre.≠tre#1

The above meta-characters alone or in combination are used to form a pattern which then are used for text mining for example tre.* means match anything 0 or more times that means now we can match tre#1 or tre.

Watch the video tutorial attached below to learn more about the fundamentals of this library.

Hopefully you found the discussion on Regex library helpful and at the end of it you must have become familiar with the way this particular library works. To learn more about python for data analysis, keep on exploring Dexlab Analytics blog, where you will always find informative posts.

Visualization with Python Part-V: Introducing the Pandas_bokeh library

Posted on September 11, 2020September 11, 2020 by Dexlab

In our fifth installment of the visualization series using Python programming language, we introduce you to another powerful library in Python that is the Pandas_bokeh library. So, let’s find out what you can achieve with Pandas_bokeh library.

Pandas_bokeh is a library which can help you create interactive graphs in python. One can zoom in, zoom out, select a certain portion of the graph to see, move the plot left, right and center, create tabs in case they want to see a single plot at a time, create multiple plots at a time, create widgets like dropdown list, check boxes, radio buttons, slider etc. It is similar to the shiny app which is used in the r programming language but simpler and faster.

How to install pandas_bokeh?

In the above code we are changing our jupyter notebook code cell into a command line by using ! and then we can use pip (python installation package) to install the library.

How to create a simple line plot using pandas_bokeh ?

The first thing to do is import the libraries which we will be using to create a line plot.

We will be creating our own dataset here and for that we need to import Numpy and Pandas libraries. Also we will be importing .figure() method from plotting module to create our canvas on which we will be building our graph from the scratch and we will also be importing .output_notebook() method to visualize our graph on jupyter notebook and to visualize our graph on a new tab and save at the same time we can use .output_file() method.
The Dataset we are creating here will have three columns ‘Days’, ‘Sales’ and ‘Date’.
We will be creating a dataset with hundred observations in each column so for that we are using .rand() method to generate hundred random numbers and that will be our ‘Sales’ column data. Now for our ‘Days’ column we will be creating a loop which will run hundred times and each time an array index value will be saved in a variable c which has an empty string and .split() method is then used to create a list of that string.
For creating a ‘Date’ column we will be using the following code
At last create a data frame we will be using .DataFrame() method.
Now to create two line graphs on a single canvas we will be using object-oriented programming.
To build the graph on the jupyter notebook we are using .output_notebook() method and in case you want to plot the graph on a new tab you can use .output_file(“filename.html”) method.

In the above line of codes we are creating two separate data frames df_d and df_d1 each containing Monday and Friday’s sales and dates separately now all we need to do is build a canvas using .figure() method and use few other arguments like x_axis_type to define the data type of the x axis and x_axis_label and y_axis_label to set graph labels, to adjust width and height of the canvas we have used plot_width and plot_height argument and to set title and title location we have used title and title_location. Once we have our canvas ready we can use .line() method and add x axis and y axis data to plot our graphs.

To interact with your graph you can use the icons on the right hand side corner which will help you zoom in and out, look at a certain part of the graph, scroll to zoom in and out, save your plot and reset the changes made by you using the side icons.

The video tutorial attached below will help you gain better understanding.

At the end of this segment you must have become familiar with the nuances of the Pandas_bokeh library. As you continue on with the series, you will realize that you are becoming an expert in visualization. On Dexlab Analytics blog, you will find interesting blogs on various topics related to Python certification training.

Visualization with Python Part IV: Learn To Create A Box Plot Using Seaborn Library

Posted on September 10, 2020September 10, 2020 by Dexlab

This is the 4th part of the series on visualization using Python programming language, where we will continue our discussion on the Seaborn library. Now that you have become familiar with the basics of the Seaborn library, you will be learning specific skills such as learning to create a box plot using Seaborn. So, let’s begin.

Seaborn library offers a list of pre-defined methods to create semi-flexible plots in Python and one of them is. boxplot() method. But what is a box plot?

Answer:- A box plot often known as box and whisker plot is a graph created to visualize the distribution of numerical data and skewness through displaying the data quartiles (or percentiles) and median.

Creating a box plot

Let’s begin by importing the Seaborn and Matplotlib library.

We will again be using the tips dataset which is a pre-defined dataset in Seaborn

Data description:- This is a dataset of a restaurant which keeps a record of the amount of bill paid by a customer, tip amount over the total bill paid, gender of the customer, whether he or she was a smoker or not, the day on which they ate at the restaurant, what was the time when they ate at the restaurant and the size of the table they booked.

To create a box plot we will be using .boxplot() method.

On the x axis we have day column having categorical data type and on the y axis we have total_bill column having numerical data type. Thus for each day with the help of a box plot we will be able to visualize how the total_bill changes around its median value.

To add title to the graph we can use. title() method from the Matplotlib library

To add color to your graph you can use palette argument

We are adding a list of palette colors in this blog down below:-

You can replace the color mentioned in the above code to see which color variations you would prefer in your graph. For example

Here we are using color palette ‘CMRmap’ to change my graph color from different shades of blues to a completely different color range i.e. from blues to orange, violet, pale yellow etc.

This tutorial hopefully, has clarified the concept and you can now create boxplots with Seaborn. Since this is a series you need to keep track of all the parts to be a visualization expert as we take you through the process step by step. Follow the Dexlab Analytics blog to access more informative posts on different topics including python for data analysis.

Go through the video tutorial attached below to get more in-depth knowledge.

Visualization with Python Part III: Introducing The Seaborn Library

Posted on September 1, 2020September 1, 2020 by Dexlab

In this 3rd part of the visualization series using Python programming language, we are going to introduce you to the Seaborn Library. Seaborn is a visualization library which is built on top of Matplotlib library in Python. This library helps us build method based plots which when combined with Matplotlib library methods lets us build flexible graphs.

In this tutorial we will be using tips data, which is a pre-defined dataset in the Seaborn library.

So let’s begin by importing the Seaborn library and giving it a sudo name sns. We will also be importing Matplotlib library to add more attributes to our graphs.

To load the tips data set we will be using .load_dataset() method.

Data description:- This is a dataset of a restaurant which keeps a record of the amount of bill paid by a customer, tip amount over the total bill paid, gender of the customer, whether he or she was a smoker or not, the day on which they ate at the restaurant, what was the time when they ate at the restaurant and the size of the table they booked.

In case while loading the dataset you see a warning box appear on the screen you don’t need to worry , you haven’t done anything wrong. These FutureWarning boxes appear to make you aware that in the future there might be some changes in the library or methods you are using.

You can simply use the .simplefilter() method from the warning library to make them disappear.

Here the category argument helps you decide which type of warning you want to ignore.

Creating a bar plot in Seaborn

Now let’s quickly go ahead and create a bar plot with the help of .barplot() method.

In the above line of code we are using column named sex on the x axis and total_bill on the y axis. But this bar plot is very different from the bar plot which we usually make. The basic concept of a bar plot is to check the frequency but here we are also mentioning the y axis data which in general is not the case with a normal bar plot, that is, we get the frequency on the y axis when we are plotting a bar graph. So what does the above code do?

The above code compares the average of the category. In our case the above graph shows that the average bill of male is higher than the average bill of female. In case you want to plot a graph showing the average variation of bill around the mean (Standard deviation) you can use estimator argument within the .barplot() to do so.

Also if you want to change the background of your graph you can easily do so by using .set_style() method.

The vertical bars between the graph are called the error bars and they tell you how far from your mean or standard deviation by max data varies.

How to add Matplotlib attributes to your Seaborn graphs

Matplotlib methods can be imported and added to the Seaborn graphs to make them more presentable and flexible. Here we will be adding a title in our graph by using .title() method from the Matplotlib library.

You can use other Matplotlib methods like .legend(),xlabel(),.ylabel() etc,. to add more value to your graphs.

The video tutorial attached below will further help you clarify your ideas regarding the Seaborn library. Follow the series to gain expertise in visualization with Python programming language. Keep on following the Dexlab Analytics blog for reading more informative posts on Python for data science training.

An Introduction to Matplotlib Object Oriented Method: Visualization with Python (Part II)

Posted on August 31, 2020August 31, 2020 by Dexlab

In the last blog that covered Part 1 of the visualization series using Python programming language, we have learned the basics of the Matplotlib Library. Now that our grasp on the basics is strong we would move further. Let’s break it all down with a more formal introduction of Matplotlib’s Object Oriented API. This means we will instantiate figure objects and then call methods or attributes from that object.

Introduction to the Object Oriented Method

The main idea in using the more formal Object Oriented method is to create figure objects and then just call methods or attributes off of that object. This approach is nicer when dealing with a canvas that has multiple plots on it.

How to make multiple plots using .add_axes()

To begin, we create a figure instance. Then we can add axes to that figure where .figure()is a method which helps us create an empty canvas and then we use .add_axes() method to give the position where the plot is to be made. The positional arguments [left, bottom, width, height] help us decide from where the graph should begin within the canvas and what should be the width and the height of the graph. Since the area of the graph is 100% (1.0), the range of the positional argument should be between 0 and 1 and in case you want to plot the graph half within and half outside the canvas, you can go beyond the specified range depending upon your needs.

Let’s quickly get to the coding part now.

In the above line of codes we are simply importing the Matplotlib library and creating a data which we want to plot.

plt.figure()method is helping us create an empty canvas and then we are giving the positional values to the .add_axes() method. As you can see we are using a variable named fig to save our canvas and then using the same variable as an object to add an axes to the canvas. Now all we need to do is use that axes to build are graph by adding x and y data.
Now you must be wondering why we aren’t able to see a plot in the corner of the canvas? It is because this procedure works only if we were to build multiple plots. So now let’s see how we can use the .add_axes() method to build multiple plots on top of each other.

In the above line of codes we are creating three axes and each axes is smaller than the other so that we are able to plot multiple graphs on top of each other.

Here we are making three different graphs and each graph has its own title and x axis and y axis labels. But to add title and axis labels we are now using .set_title(), .set_xlabel(), and .set_ylabel() instead of .title(), .xlabel() and .ylabel(). In axes2.plot() we are also using RGB color instead of using the predefined color in .plot() method. You can use your favorite color too by simply typing RGB color picker in your Google search and copy pasting the color code in the .plot() method. After running the above code we get the following graph:-

How to make multiple plots using .subplots()

.subplots() method is similar to the previous .subplot() method, the only difference is that now we use it on a canvas.

In the .subplots() we do not mention the plot number instead we use plot indexing method to build graph.
As you can see we are accessing the index number to build our plot and then using .tight_layout() method to keep the graphs from overlapping. After running the above code we get the following graphs:-

Do not forget to check out the video tutorial attached below to learn how this method works. Keep following the series to upgrade your skills and to explore more informative posts on topics like Python Programming training you need to follow the Dexlab Analytics blog.

A Quick Guide To Using Matplotlib Library (Part I)

Posted on August 27, 2020August 31, 2020 by Dexlab

Matplotlib is the “grandfather” library of data visualization with Python. It was created by John Hunter. He created it to try replicating MatLab’s (another programming language) plotting capabilities in Python. So, if you are already familiar with matlab, matplotlib will feel natural to you.

This library gives you the flexibility to plot the graphs the way you want. You can start with a blank canvas and plot the graph on that canvas wherever you want. You can make multiple plots on top of each other, change the line type, change the line color using predefined colors or hex codes, line width etc.

Installation

Before you begin you’ll need to install matplotlib first by using the following code:-

There are two ways in which you can built matplotlib graphs:-

Method based graphs
Object-oriented graphs

Method Based Graphs in Matplotlib:-

There are pre-defined methods in matplotlib library which you can use to create graphs directly using python language for example:-

Where, import matplotlib.pyplot as plt this code is used to import the library, %matplotlib inline is used to keep the plot within the parameters of the jupyter notebook, import numpy as np and x = np.array([1,3,4,6,8,10]) is used to import the numpy (numerical python) library and create an array x and plt.plot(x) is used to plot the distribution of the x variable.

We can also use .xlabel(), .ylabel() and .title() methods print x axis and y axis labels and title on the graph.

If you want to add text within your graph you can either use .annotate() method or .text() method.

Creating Multiplots

You can also create multiple plots by using .subplot() method by mentioning the number of rows and columns in which you want your graphs to be plotted. It works similar to the way you mention the number of rows and columns in a matrix.

You can add title, axis labels, texts etc., on each plot separately. In the end you can add .tight_layout() to solve the problem of overlapping of the graphs and to make the labels and scales visible.

Check out the video attached below to get an in-depth understanding of how Matplotlib works. This is a part of a visualization series using Python programming language. So, stay tuned for more updates. You can discover more such informative posts on the Dexlab Analytics blog.

Data Warehouse: Concept and Benefits

Posted on August 24, 2020August 24, 2020 by Dexlab

A business organization has to deal with a massive amount of data streaming from myriad sources, and data warehousing refers to the process of collection and storage of that data that needs to be analyzed to glean valuable business insight. Data warehousing plays a crucial role in business intelligence. The concept originated in the 1980s, it basically involves data extraction from disparate sources which later gets processed and post formatting the data stays in the system ready to be utilized for taking important decisions.

Data warehouse basically performs the task of running an analysis on the stored data which could be both structured and unstructured even semi-structured, however, the data that is in the warehouse cannot be modified. Data warehousing basically helps companies gain insight regarding factors influencing business, and they could use the data insight to formulate new strategies, developing products and so on. This highly skilled task demands professionals who have a background in Data science using python training.

What are the different steps in data warehousing?

Data warehousing involves the following steps

Transactional data extraction: In this step, the data is extracted from multiple sources available and loaded into the system.

Data transformation: The transactional data extracted from different sources need to be transformed and it would need relating as well.

Building a dimensional model: A dimensional model comprising fact and dimension tables are built and the data gets loaded.

Getting a front-end reporting tool: The tool could be built or, purchased, a crucial decision that needs much deliberation.

Benefits of data warehousing

An edge over the competition

This is undeniably one benefit every business would be eager to reap from data warehousing. The data that is untapped could be the source of valuable information regarding risk factors, trends, customers and so many other factors that could impact the business. Data warehousing collates the data and arranges them in a contextual manner that is easy for a company to access and utilize to make informed decisions.

Enhanced data quality

Since data pooled from different sources could be structured or, unstructured and in different formats, working with such data inconsistency could be problematic and data warehousing takes care of the issue by transforming the data into a consistent format. The standardized data that easily conforms to the analytics platform can be of immense value.

Historical data analysis

A data warehouse basically stores a big amount of data and that includes historical data as well. Such data are basically old records of the company regarding sales, employee data, or, product-related information. Now the historical data belonging to different time periods need to be analyzed to predict upcoming trends.

Smarter business intelligence

Since businesses now rely on data-driven insight to devise strategies, they need access to data that is consistent, error-free, and high quality. However, data coming from numerous sources could be erroneous and irrelevant. But, data warehousing takes care of this issue by formatting the data to make it consistent and free from any error and could be analyzed to offer valuable insight that could help the management take decisions regarding sales, marketing, finance.

High ROI

Building a data warehouse requires significant investment but in the long term, the revenue that it generates can be significant. In fact, keen business intelligence now plays a crucial role in determining the success of an organization and with data warehousing the organizations can have access to data that is consistent and high quality thus enabling the company to derive actionable intel. When a company implements such insight in making smarter strategies, they do gain in the long run.

Data warehousing plays a significant role in collating and storing valuable data that fuels a company’s business decisions. However, given the specialized nature of the task, one must undergo Data Science training, to learn the nuances. The field of big data has plenty of opportunities for the right candidates.

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