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numpy Python Python Tutorial 

What is an array in Python?

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Estimated reading time: 3 minutes

Python arrays are used to manage how data is analysed and have the data in a structured form for the data analyst or data scientist to use.

What is an Array?

An array has the following properties:

  1. The data in it is of the same data type.
  2. The data is stored as contiguous memory locations, meaning meaning the lowest value is at index 0 and the last value is at the highest index value.
  3. Arrays assign index values to each data point contained within it.
  4. You can append values to the array.
  5. You can delete values from the array, that is it is mutable.

What are the differences between arrays and lists?

For the most part arrays and lists are the same, but with one difference:

A list can store any data type you want e.g. strings, integers etc.

On the other hand, arrays can only store data that is of the same data type.

What are the different ways that I can create an array?

(A) Use Numpy 

import numpy as np

a = np.array([1,2,3])

print(a)
print(type(a))

Output:
[1 2 3]
<class 'numpy.ndarray'>

(B) Use array

import array as test_array

a = test_array.array('i',[1,2,3])

print(a)

Output:
array('i', [1, 2, 3])
<class 'array.array'>

On the Python.org website, below are the list of values that can be populated into the above program, depending on what your need is:

When should I use arrays?

It really depends on the nature of your python program, but below are some examples that may help you make a decision:

(A) Many variables of the same type : There maybe a scenario where you have to create an array to store data that is of the same data type. For example you have a list of codes to look up against, which are all integers.

(B) Faster and more efficient : If speed is what you are looking for using arrays, will help improve performance of your computer program, using lists is much slower.

(C) Compactability and efficiency : If the nature of your program needs to store large amounts of data that needs to be accessed quickly , then this would be a good reason to use them.

(D) Ability to retrieve data quickly through indexing: As arrays have index values associated with them, they data can be easiy retrieved.

(E) Need to compute some mathematical values: Arrays are excellent for any numerical operations you need to complete, as the level of coding is minimal.

import array as test_array

a = test_array.array('i',[1,2,3])

mydivider = 2

mynewlist = [x / mydivider for x in a]
print(mynewlist)

result:
[0.5, 1.0, 1.5]

So in summary:

Speed , efficiency and ease of use are the main reasons to use an array.

We use arrays here in how to show percentage differences between files in python , why not go over and see it in action!

class Python 

how to create an instance of a class

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Estimated reading time: 1 minute

Here in how to create an instance of a class, as described herein, how to create a class in Python, we will further explore the instance of class and how this can be used within a program to assign values to an object. This allows that object to inherit those values contained within the class, making it easier to have consistency regards functionality and data.

This video covers off

(a) creating an instance of a class

(B) Using the __init__ within the class

(C) define the constructor method __init__

(D) Creating an object that calls a class and uses the class to process some piece of data.

What are the benefits of this?

  • You only need to create one class that holds all the attributes required.
  • That class can be called from anywhere within a program, once an instance of it is created.
  • You can update the class, and once completed, those new values will become available to an instance of that class.
  • Makes for better management of objects and their properties, not multiple different versions contained within a program

 

 

class Python 

How to create a class in Python

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Estimated reading time: 1 minute

How to create a class in Python: In this video explaining classes will be the main topic on how they are constructed,  explain how to create an instance of a class.

When talking about classes, they can also be referred to as object-orientated programming.

Also, we look at what class attributes are and how they can be used to assign key data that can be called anywhere within a program.

The steps involve the following:

(a) Create a class

(B) Assign attributes to the class

(C) Create a method within the class ( similar to a function)

(D) Create an instance of a class to call its attributes and methods.

This video is a follow on from object oriented programming – Python Classes explained

Python regular expressions 

Regular expressions python

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Estimated reading time: 3 minutes

Regular expressions explained

Regular expressions are a set of characters usually in a particular sequence that helps find a match/pattern for a specific piece of data in a dataset.

The purpose is to allow a uniform of set characters that can be reused multiple times, based on the requirements of the user, without having to build each time.

The patterns are similar to those that you would find in Perl.

How are regular expressions built?

To start, in regular expressions, there are metacharacters, which are characters that have a special meaning. Their values are as follows:

. ^ $ * + ? { } [ ] \ | ( )

.e = All occurrences which have one “e”, and value before that e. There can be multiple e, eg ..e means check two characters before e.

^ =Check if a string starts with a particular pattern.

*  = Match zero or more occurrences of a pattern, at least one of the characters can be found.

+ = Looks to match exact patterns, one or more times, and if they are not precisely equal, then nothing is returned.

? =Check if a string after ? exists in a pattern and returns it. If a value before the ? is directly beside the value after ? then returns both values.

—> e.g. t?e is the search pattern. “The” is the string. The result will return only the value e, but if the string is “te”, then it will return te, as the letters are directly beside each other.

da{2} = Check to see if a character has a set of other characters following it. E.g. sees if d has two “a” following it.

[abc] = These are the characters you are looking for in the data. Could also use [a-c] and will give you the same result. Change to uppercase to get only those with uppercase.

\ = Denoting a backslash used to escape all metacharacters, so if they need to be found in a string, they can be. Used to escape $ in a string so they can be found as a literal value.

| = This is used when you want an “or” operator in the logic, i.e. check for one or more values from a pattern, either or both can be present.

() = Looks to group pattern searches or a partial match, to see if they are together or not.

 

Special sequences, making it easier again

\a = Matches if the specified characters are at the start of the string been searched.

\b = Matches if the specified characters are at the beginning or the end of the string been searched.

\B = Matches if the specified characters are NOT at the beginning or the end of the string been searched.

\d = Matches any digits 0-9.

\D = Matches any character is not a digit.

\s = Matches where a string contains a whitespace character.

\S = Matches where a string contains a non-whitespace character.

\w = Matches if digits or character or _ found

\W = Matches if non-digits and or characters or _found

\z = matches if the specified characters are at the end of the string.

 

 

For further references and reading materials, please see the below websites, the last one is really useful in testing any regular expressions you would like to build:

See further reading material here: regular expression RE explained

Another complementary page to the link above regular expression REGEX explained

I found this link on the internet, and would thoroughly recommend you bookmark it. It will also allow you to play around with regular expressions and test them before you put into your code, a very recommended resource Testing regular expressions

 

Python Python Tutorial 

Python tutorial: Create an input box in Tkinter

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Using an tkinter input box for your data projects

There may be an occasion as you are building out a data science or data analytics project, checks need to be performed on the dataset as follows:

  •  Big data sets and speed requirements in conjunction with
  • The need to reduce the volume of data returned which is impeding performance

and this is where input boxes and Tkinter can help!

In the below video, we are demonstrating an introduction to using an input box and validating the input.

We demonstrate how to validate the data entered into the tkinter input box and return a message, this will ensure the user gets the correct data.

Types of uses for a tkinter input box are varied, here are some thoughts:

  • Use an input box to return a set of data for a particular day.
  • Using them to filter down the results to a particular cohort of data.
  • Conduct a string search to find data quality issues to be fixed.
Python Python Tutorial 

Python tutorial: How to create a graphical user interface in Tkinter

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How would you like to present your data analytics work better?

When starting your data analytics projects, one of the critical considerations is how to present your results quickly and understandably?

Undoubtedly this is true if you are only going to look at the results yourself.

If the work you do is a repeatable process, a more robust longer-term solution needs to be applied, this is where Tkinter can help, which is a python graphical user interface.

When you are importing tkinter, some of the functionality that can be used include:

  • Use them to build calculators.
  • They can show graphs and bar charts.
  • Show graphics on a screen.
  • Validate user input, through building entry widgets.

Where this all fits in with data analytics?

While going through a set of data and getting some meaning to it can be challenging, using the python graphical user interface tutorial below can help build the screens that will allow a repeatable process to display in a meaningful way.

Using the tkinter widget could help achieve the following:

  • Build a screen that shows data analytics errors in a data set, e.g. The number of blank column values in a dataset.
  • Another application is to run your analytics to show the results on a screen that can be printed or exported.
  • Similarly, you could also have a screen where a user selects several parameters that are fed into the data analytics code and produces information for the user to analyse.

There are many more ways that you could do this, but one of the most important things is that data analytics can be built into a windows environment using Tkinter.

These GUI applications are what the user would be used to currently seeing. As a result, this could help to distribute a solution across an enterprise to lots of different users.

Also, another benefit is that they will work on many different operating systems.

The only thing that needs to happen is that the requirements the user needs are defined, and the developer then builds on those, with the data analytics code run in the background of this program with Tkinter and output into a user-friendly screen for review.

Python Python Tutorial 

How to create a combobox in tkinter

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Estimated reading time: 2 minutes

Here we have delivered a complimentary video on How to create a graphical user interface in Tkinter .

It will demonstrate how a Combobox can be used to select values and then validate the entry chosen.

Using a Combobox in the computer programming world has been around for some time.

It is a useful way to select from a choice and could in many ways in data analytics help as the following examples show:

  • Select a date to filter a data set down to values that are in the dataset.
  • Using matplotlib to plot data points in charts, you could have dynamic values that change the diagram based on values chosen from the Combobox.
  • Utilizing data analytics reports that the user accesses, the Combobox could be used to change the data shown dynamically to allow comparisons.
  • When looking to fix data quality issues, use the Combobox to select values for a date that needs to be fixed, apply the fixes on screen, and then save back to the database.

Developing a Tkinter GUI and the possibilities it brings

In this video, we use ttk, written to help split the behavior of code from the code implementing its appearance.

You can see plenty more on it here ttk information. This is a handy piece of functionality as styling an object can interfere with how it works.

We also have a function that helps with the validation. In the below, it accomplishes the following:

  • Allows the combobox value selected to be retrieved.
  • Validates the entry chosen in the combobox using an if statement.
def checkifireland ():
    x = combolist.get() # asssigns the value inside the combobox to x so it can be processed
    if x == "Ireland":
        messagebox.showinfo("Correct answer", "You will love it in Ireland")
    else:
        messagebox.showinfo("Incorrect answer", "You should visit Ireland first!")

The effectiveness is especially handy as it helps to ensure that the code returned from the Combobox to the function is correct

The below video will take through this step by step and explain the concepts discussed above.

The next steps

There are many informative Python – working with excel videos that are on our YouTube channel.

We are looking to bring them in and show them on a graphical user interface tutorial.

To see how to load a set of values into a combobox from an SQLite database table, have a look at how to load values into a combobox

R Programming 

how to remove unwanted characters from your data

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Using r programming functions to cleanse data
In our recent post  Python Tutorial: How do I remove unwanted characters  we walked through the concepts behind data cleansing.

We demonstrated several different approaches to data cleansing, and the use of regular expressions was also shown.

Here we look at that approach using rstudio and the following functions:

How to approach data cleansing

In removing unwanted characters, you want to ensure that you have a defined list of what should not appear and will cause you errors. It is also essential to understand the type of data errors that can occur as follows:

  • Data entry errors
  • Data columns have the incorrect format, e.g. Telphone numbers which have non-numerical characters in them
  • Missing data that is required – e.g. null values
  • Data that does not make sense, e.g. date of birth that is beyond the range of what you would typically expect to see
  • Duplicate values for the same piece of data. The problem here is that this can inflate the no of data errors, and not give a true count of the actual errors.

In the below video we utilise r programming code using the above functions, but also use an if statement to check if an unwanted character is in the data set first before proceeding to remove it and return the cleansed data.

Some of the strategies to help counteract data errors could include:

  • Eliminate manual inputs
  • Controls at point of entry for data, e.g. for dates only allow date formats in the field.
  • Reduce duplication of the data across multiple systems, reduces the no of places that data differences can occur.
  • If integrating different systems with the same data into one network, perform a data cleanse beforehand, reduces the work needed afterwards to clean up the problems that brings.

 

Python 

Tkinter python tutorial

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Estimated reading time: 3 minutes

Let’s make the introductions 🙂
Tkinter is a package that allows a programmer to build a GUI interface, which then can be opened on a computer screen by a user. There are many different types of GUI apps, but examples include a calculator or a text editor that opens when you click it.

Tkinter would be the most commonly used GUI package in Python, due to its simplicity, but PySimpleGUI, PYQt or PySide are other alternatives. Ensure you research these before using to make sure they suitable for your needs.

Why use Tkinter?

  • Relatively simple and easy to learn, upskilling is quick.
  • A great introduction to the concepts and ideas for building GUI apps, you will get a good grounding in the techniques and approaches needed.
  • Very well documented, so a programmer should be able to find the answer to anything specific they need to understand.

Now we are introduced, let’s see how to utilise it:

Install Python as usual, and make sure that Tkinter is working and you have the correct version. Note that import tkinter is for version 3.x, before that use import Tkinter

Please note that you will see in places when using Python code, that capitalization is important. This will sometimes puzzle you as to why some of your code does not work, usually, the interpreter should flag it for you.

While it is correct to put a capital at the start of a line, the programming language will ignore written English convention. An example is as follows:

list = ['a','b','c']
Print(list)
gives 
NameError: name 'Print' is not defined
whereas
list = ['a','b','c']
print(list)
gives ['a', 'b', 'c'] 
No errors

When saving your python script DO NOT call it tkinter.py as I did, the import statement will not work. Call it something like tkinter_test.py, see red arrow below.

At the start of the video below the code will look like this. the first six lines are the creation of the Tkinter screen its size and any buttons that will appear on it.

Note that all code should appear betwee line two and line six, so that the screen output works and looks correctly.

Added to this code in the following video:

  • Button – which will open our YouTube channel
  • An image
  • A clickable link – Which will bring you to our Home Page

A screenshot of the final output is as follows:

See a link to the Python documentation here Tkinter on python.org

Definition 

Recursion

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Estimated reading time: 2 minutes

What is recursion?
To start a recursion is looking to solve a problem, by breaking it down into smaller chunks, which contribute to the final answer.

If it is calling itself, then it is commonly known as a recursive function.

By breaking down the problem at hand, it can then lead to a quicker understanding and solution to the problem.

A simple example might help here, explaining through factorial:

4! = 4*3*2*1 = 24
simple factorial example

From studying maths at school, the simple example above breaks down as:

  • The result 24 is a product of all the values from 4 down to one.
  • As each value that makes it up is known, it then can be seen how the result is made up.
  • The above can be viewed as a recursive function as it keeps repeating on itself until it reaches one, the base.
  • The recursion knows there are three steps before it reaches one; this is where the breakdown into smaller chunks comes in.

So it could be broken down as follows:

Step 1
4*3 ---> Not reached one, try again from the start.
Step 2
4*3*2 ---> Not reached one, try again from the start.
Step 3
4*3*2*1 ---> Reached one, so the recursion stops and the result is outputted.

Steps 1 to 3 are the steps within the function it takes until it reaches the base value, where the function stops and outputs the final value calculated.

Attributes of a recursion

  • A function which calls on itself, this is the repeated steps above until it reaches the base of 1, meaning it doesn’t loop infinitely.
  • Must be possible to break the problem down into smaller parts.
  • As the problem gets broken down, it must become easier to solve without further calculations.
  • Once a smaller part has calculated, this just becomes part of the answer to the overall problem.

Things to watch out for when using recursion

  • Ensure you always have a base value; without it, you could encounter an infinite loop.
  • Not having the ability to break up the problem into smaller steps won’t allow the calculation of the final answer.

Why use recursion?

  • It helps to break up a complicated task into smaller bits.
  • Assists a programmer to see what steps have already coded for so can be solved with other functions already written.
  • Where there are multiple recursive functions, allows to see if similarities in steps, hence only need to programme once for them.

A good source to provide further knowledge can be found here Wikipedia – Recursion

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