DEV Community: Priscillah Nalubega

JavaScript FUNCTIONS

Priscillah Nalubega — Mon, 11 Oct 2021 17:23:56 +0000

Understanding functions is so crucial when learning any programming language and it isn’t any different when it comes to JavaScript. JavaScript has a diverse use of functions and one them are their use in the place of special syntax for object-oriented programing found in other programming languages. In this article we are going to discuss the following:

How to define and use a function
Passing parameters to a function
Pre-defined functions that are available to you
The scope of variables in JavaScript
The Concept that functions are just data

Before we dive into the soup, I will assume that you have an understanding of computer basics, HTML and CSS basics as well as some basics in JavaScript.

With all that in mind let’s dive into the wonderful world of JavaScript Functions.

What is a function?

A function is a block of code with a name, and since it has a name it can be reused over and over again.

Function Declaration

A function declaration also known as a function statement is made up of:

The Function Statement with the function keyword
The name of the function
A list of parameters(arguments) to the function enclosed in parentheses and separated by commas.
The body of the function which contains the code
The return statement which gives the out put of the function
The JavaScript Statement that defines the function, enclosed in curly brackets.

For example:

 Function sum ( a, b ){
      Let c = a + b;
      return c;
}

The Function sum takes two parameters, a and b. The function consists of two statements; one that declares a new variable c and assigns it the sum of a and b and the other statement that returns the value of c. The statement return specifies the value returned by the function. Primitive (such as number) parameters are passed to the functions by value. If you pass an object as a parameter and the function changes the objects properties, that change is visible outside the function.

Function Expressions

A function can also be created using function expression. Such a function doesn’t necessarily need to have a name like the latter way of declaring functions. For example:

const sum = function(a, b){
       let c = a+b;
       return   c;
}
console.log(sum(3, 5)) // 8

Inorder to make debugging easier a name can be given to a function for example:

const sum = function add(a, b){
     return a + b;
}
Console.log (sum (4, 5)) // 9

Calling a Function

Now that we have glanced into what a function is and how it is declared, let’s now see how we can execute these functions. Calling the function actually performs the specified actions with the indicated parameters as defined when declaring the functions. You could call it as follows ;

sum(2,5); // 7

This statement calls the function with arguments of 5,5. The Function excutes its statements and returns the value of 10 .

Parameters

If you are to recall what we have discussed in the previous section, when declaring a function you specify the parameters the function expects to receive when it’s called in the parentheses. A may not require any parameters but when it does and you forget to pass them, JavaScript will assign the value undefined to the one that you didn’t fill in. For example;

function sum( a, b){
    let c = a + b;
    return c;
}
sum(4); // NAN

The function call will return NAN (Not A Number) because it tries to sum 4 and undefined. Therefore, make sure you pass a function with correct values and the correct number of values.

Pre-defined functions in JavaScript

Let’s have a look at some of the in-built functions in JavaScript available for to use.

parseInt ()
parseFloat ()
isNaN ()
isFinite ()
eval ()

parseInt ()

parseInt () takes any type of data and converts it into an integer. If it fails it returns NAN. For example

parseInt (‘1234’)  // 1234
parseInt (‘ABC123’)  // NAN
parseInt (‘1234AB’)  // 1234

parseFloat ()

parseFloat () is similar to parseInt() but also looks for decimals when trying to figure out a number from your input

parseFloat (‘123’) // 123
parseFloat(‘1.23’) // 1.23
parseFloat(‘1.34abc.00’) // 1.34
parseFloat (‘a.123.bcd’)  // NAN

Both parseInt () and parseFloat () give up at the first occurance of an unexpected character, like a letter even though the rest of the string might be numbers.

isNAN ()

isNAN () is used to check whethe the input value is a valid number that can be used safely in an arithemetic operation. This is another convenient way of verifying whether the function parseInt and parseFloat succeed.
For example;

isNAN (NAN) // true
isNAN (123)  // false
isNAN (1.34)  // FALSE

isFinite ()

isFinite () checks if An input is a number that is neither inifinity nor NAN.
For example:

isFinite (infinity) // false
isFinite (12) // true
isFinite (egrye123) // 
isFinite(11gttf345) // true

eval ()

eval () takes a string input and executes it as JavaScript Code;

eval (‘let i = 2;’)
i; // 2

However you should avoid executing JavaScript from a string as it imposes an enormous risk.

Scope of Variables

In JavaScript variables are defined in a function scope, meaning that variables defined inside a function cannot be accessed from anywhere outside the function since that variable is defined only in the scope of the function. In contrast, a function defined in global scope can access all variables defined in the global scope.

let global= 12;
function func(){
         let local =2;
          global ++;
         return global;
}
func(); // 2
func(); // local

At this point, you now have a profound understanding of JavaScript Functions. This article lays a foundation that will allow you to grasp advanced JavaScript concepts like object oriented JavaScript and patterns. Till next time, thank you for reading

SIMPLE BLOG APP

Priscillah Nalubega — Thu, 26 Aug 2021 20:31:32 +0000

SIMPLE BLOG APP

This is a simple blog app where users can:

Register and login into the app
See posts
Create posts
Update posts
And delete posts

The user can also logout of the app

Requirements

To be able to run the the program on your local machine you should have the following

note: its been tested on windows 10, python 3.9.6

install a virtual environment
install flask
install wtforms for the login and registration forms
sqlalchemy for the database
install bcrypt to hash the passwords

Setting up the environment

install a virtual environment on your windows machine: In your Windows command shell prompt type in:

pip install virtualenv

Once inside the project folder run:

virtualenv <env>

the activate your virtual environment:

.\<env>\Scripts\activate

To Run the code

still in your virtual enviroment:

set FLASK_APP=run.py

then

flask run

you will now be able to explore the app on your local machine

the source code to the app is here

thanks for reading.

Python Boot Camp Experience!!!

Priscillah Nalubega — Tue, 10 Aug 2021 14:13:02 +0000

Friday 6th August, 2021, made the end of week the of the python boot camp at lux tech academy. For so long I have been trying to learn python on my own and most of the times it ends fatally. The constant bugs, indention errors almost made me give up learning python entirely but that's all part of the learning process. In my recent quest to master programming, a friend of mine referred me to the lux tech academy boot camp where have learnt and familiarized my self with a lot of new stuff thus being a beginner for the nth time now.

Though my experience cannot be limited to what am going to list down it doesn’t stop me from sharing a few lessons.

INTRODUCTION

Week one commenced with a variety of talks from how to be abadass python developer to setting up the environment and writing clean code. I learnt the professional way of writing python code that using the pep8 standard. To make my learning easier I used Python Tutorial website for reference. Scrimba is also a nice place to start on your journey of being a python developer. I also learnt how to write and publish technical articles

Hello world!

As our mentor during the program always quotes "if you can write “hello world” you can change the world" we commenced with learning the basics of the python language which included the syntax, data types, key-words and styles of writing python code. At the end of the week I able to build a random password generator.

Happy coding

The happy phrase that sends off all programmers into the deep waters of writing code. During the second week of the boot camp i learnt

lists, tuples, dictionaries and sets
Functions
mutable and immutable
common methods in python
Data structures and alogorithms

With that I was able to build a youtube downloader though faced a lot of challenges with the pytube package.

Eat, code, sleep,

In week 3 we where Demystifying The Flask Application factory pattern at the end of which I was able to build a simple flask application.

Conclusion

I believe that by the end of the boot camp my confidence as a software developer would have been boosted. The things I have learnt in this boot camp cant be limited to what I have shared but this all I can say for now.
thanks for reading, till next time chawwww!!!

Introduction to Python Functions!!

Priscillah Nalubega — Sat, 31 Jul 2021 16:07:11 +0000

Functions are named blocks of code that are designed to do one specific code. Functions facilitate reusability of code. When you want to do something repeatedly you define a function and call it whenever you need it.

Built-In Functions

Python comes with several built-in functions that you can use to create wonderful programs. Here are a few but not limited to built-functions.

print()	range()	input()	list()
next()	round()	max()	tuple()
str()	dic()	sorted()	type()
object()	sum()	set()	eval()

Creating a function

In python a function is defined using the def keyword for example:

def greet():
    print("Hello World")

Calling a function

The above function definition is inert until the the function is triggered or called. when you call the function:

greet() # Hello World

Arguments

Arguments refer to the information that is passed into the function Arguments are specified after the function name, inside the parenthesis. You can add as many arguments as you want but you have to separate them with a comma. for example:

def greet(name):
    print( "Hello" +" "+ name)
greet("John") # Hello John

Positional Arguments

Because a function can have multiple parameters, a function call may need multiple arguments.You can use positional arguments which need the same order the parameters were written. This is how it works:

def greet(name , place):
    print( f" Hello {name} from {place}")
greet( John, Uganda) # Hello John from Uganda

Now imagine a situation when then name and the place are swapped when the function is called.

greet(Uganda, John) # Hello Uganda from John

And this quite doesn't make sense. This means that the first argument in the function call is used as the value of the first parameter and the second argument in the function call is used as the value of the second parameter. To avoid such such situations from happening when can specify both the arguments and parameters together with the values that they take. These are called Keyword arguments. Here the order of the arguments in the function call doesn't matter as long as the names of the parameters are correct.

Now we have:

greet(place ="Uganda", name="John") # Hello John from Uganda

Arguments and Parameters

A parameter is the variable listed inside the parentheses in the function definition. An argument is the value that is sent to the function when it is called.

Number of Arguments

By default, a function should be called with correct number of arguments. Should call a function with more or less arguments than it expects it will bring an error.

for example:

def greet(name, place):
  print("Hello" + " " + name +" "+ place)

greet("Jack", "Ghana") # Hello Jack from Ghana

If you try to call this function with 1 or 3 arguments

greet("Jack")

You get this error:

Traceback (most recent call last):
  File "demo_function_args_error.py", line 4, in <module>
    greet("Jack")
TypeError: greet() missing 1 required positional argument: 'place'

Default Value Parameter

When writing a function, you can define a default value for each parameter. If an argument for a parameter is provided in the function call, Python uses the argument value. If not, it uses the parameter’s default value. So when you define a default value for a parameter, you can exclude the corresponding argument you’d usually write in the function call.

def people(country = "Kenya"):
  print("I am from " + country)

people("Sweden")
people("Burundi")
people("Ghana")
people("Nigeria")

Return Values
To let a function return a value, use the return statement:

def sum(x):
  return 4 + x

print(sum(1)) # 5
print(sum(3)) # 7
print(sum(10)) # 14

In conclusion, we have covered:

what are functions
Built-in functions
how to define functions
calling functions
Arguments
the difference between arguments and parameters
Return values

Python Basics! Python 101!

Priscillah Nalubega — Sat, 24 Jul 2021 04:47:02 +0000

Python is an incredibly versatile, expansive language which due to its similarity to every day languages, is surprisingly easy to learn among inexperienced programmers. Python is very popular among professionals and students because it has a clear and simple syntax that will get you writing useful programs in short code. It even has an interactive mode, which offers immediate feedback, allowing you to test out new ideas almost instantly and has plenty of libraries allowing programmers to get a lot done with relatively little code.

Some of python's applications include:

Python is used in most of the search engines
Enables banks to track the money in their accounts
Used to program machines that are used to perform tricky medical procedures in hospitals.
Desktop applications
Web development
Automation

Getting started with python

As you can see python is quite handy now let’s get started. To install windows on your system visit the python website. Here and click on the latest version of Python for Windows. The installer file will download automatically. Of the different installer options, select “executable installer”. Double-click the installer file to install Python. Choose “install for all users” and click “next” at each prompt, without changing the default settings.
When the installation is finished, check that it was successful by opening the IDLE program. Go to the “Start” menu, choose “All Apps”, and then select “IDLE”.

On a mac

Go to the Python website.Here and click on “Downloads” to open the download page.From the downloads options, click on the latest version of Python 3 that matches your operating system. The Python.pkg file will download to your Mac automatically. Install python. You’ll find the .pkg file in the “Downloads” folder. Its icon looks like an opened parcel.Double-click it to start the installation. At the prompts, click “Continue” and then “Install” to accept the default settings. Open IDLE. When the installation is finished, check that it was successful by opening the IDLE program. Open the “Applications” folder, and then the “Python” folder. Double-click “IDLE”

Your first program in python

This is now the time to get our hands dirty and what better way than the programmers best friend “hello world”.

First create a new folder where you will be saving your python files, python you wouldn’t want your files flying about the home directory. Then, launch the vs code and locate your new folder.
In Vscode install the python extension and then create a file called hello_world.py, enter the following command and then save.

Print(‘hello World’)

Print () is an in-built python function that displays a message on the screen. In our example it will output ‘hello World’

Executing the python program

To execute our program click the run button and the output will be displayed in the terminal. The message that will be seen on the screen is

hello World

Note that you are more or less familiar with python lets dive into the basic syntax

Python basic syntax

Keywords are words that python reserves for defining the syntax and structure of the python language. Hence, you cannot use them as a regular identifier when naming variables, functions, objects, classes, and similar items or processes. They include but not limited to:

and	assert	break	for	not	is
lambda	else	from	finally	pass	for
raise	None	False	del	if	import

All the keywords except True, False and None are in lowercase and keywords are case sensitive.
An identifier is a name given to a variable, class, function, string, list, dictionary, module, and other objects.

Rules for writing identifiers

Identifiers can be a combination of letters in lowercase or uppercase or digits and an underscore. E.g p, P lowercase, UPPERCASE, python_basics1
An identifier cannot start with a digit.
Key words cannot be used as identifiers.
An identifier cannot contain special characters e.g ‘#@$%
An identifier can be of any length.

Naming Global Variables

Global variable names should be written in lowercase. Names consisting of two or more words should be separated by an underscore.

Naming Classes

The CamelCase convention is used when naming a class.

Naming instance Variables

Instance variables consisting of several words should be separated by an underscore and variable names should be in lowercase

Naming modules and Package Names

Names for modules should be in lower case, they should be short one-word

Naming functions

Function names should be in lowercase and those with several words should be separated by an underscore

Naming Constants

Constants are written in all uppercase letters and underscores are used to separate those with several words

Comments

Comments are notes used to explain the code in the program and cannot be seen by the user running the program but can be seen in the source code. Comments make it easy for you and other programmers to evaluate your work many years after the code was written.

#single line comment
'''
multiline comment
using a doctstring
'''

Variables and Data Types in python

Variables

A variable is a reserved memory location that can be used to store values. This means that when you create a variable you reserve some space in the memory. You can declare a variable using an appropriate name and assigning a variable to it using the assignment operator (=)

student ="John smith"
age = 20
amount = 20.05
paid = False

You don’t need to tell python that a variable should contain a specific type of data. Python automatically identifies the data type based on the values you assign to the variable.

Data types

1). strings
A string is an ordered series of Unicode characters which may be a combination of one or more letters, numbers, and special characters. It us an immutable data type which ,means that when its created it cannot be changed.

single_string = 'this is a single string'

multiline_string ='''
                    like
                   this
                   example
                   '''

#for escaping characters
esc_string = "The teacher said:\ "You are a genuis.\""
print(esc_string) # The teacher said: "You are a genuis"

#concatinate stringg
greet ="hello"
name ="john"
print(greet+ ""+ name)# hello john

#interpolation
# method 1
name = "John"
age ="20"
message= f"{name} is {age} years."

#method 2
name = "John"
age ="20"
message = '{}is {}years.formart(name,age)'

#method 3
name = "John"
age ="20"
message = '{} is {}.format(first=name, last=age)'

#accessing characters in a string
name = "John Smith"
print(name[0])#J
print(name[6:9])#Smith

2.) Number Data types
There are 3 numeric data types in python i.e int, float and complex

normal_integers = 46
floating_point_numbers = 50.04
complex_numbers = 3 +5i

# converting from one numerical Type to Another
float(56)
int(3.0004)
complex(45)

Arithmetic Operators

print(3+2) # 5 (addition)
print(10-5) # 5 (subtraction)
print (3*6) # 18 (multiplication)
print(46/2) # 23 (division)
print(3**3) # 9 (exponent)
print(11%4) # 3 (modulus)
print(60//4) # 15 (floor division)

3). Booleans

d= True
b= False

4). Lists
A list is one of the most commonly used sequences and it is the most flexible type. It can hold one data type or a combination of several data types. A list is mutable that is you can add, remove or modify its elements.

# can create a an empty list with this syntax 
my_list =[]

# lists with integers
num_list = [1,2,3,4,5]

# list with strings
string-list = ["John", "Mary", "Peter"]

# list with mixed data types
mixed_list = ["John", 24, True]

# methods on lists
children = ["John", "Mary", "Sophy", "Peter"]
# append
children.append("Jerry")

# insert
children.insert(2,"Tom")

# remove
children.removed("Sophy")

# get length
print(len(children)) # 5

5). Tuples
Tuples are just the reverse of lists. They are immutable and surrounded by ().

new_tuple  = ("a","b","c","d","e")
print(len(new_tuple)) # 5
print(new_tuple[3]) # d

6). Dictionaries
This is unordered collection of key-value pairs which are separated by a colon , and enclosed in curly braces {}. A dictionary can contain any data type and is mutable however its keys are immutable and can only contain numbers, tuples and strings

ages= {
"John": 20,
"Mary":21,
"Tom":25,
"Jerry":19
}

# access, modify, delete

print(ages[Mary]) # 20
print(len(ages))  #  4

This marks the end of our introduction, I hope by now you know what python is why choose python, applications of python and how to install it on your machine. We have gone through how to save python files and execute them, the basic syntax in python and the various data types. Thank you for reading

DEV Community: Priscillah Nalubega

JavaScript FUNCTIONS

What is a function?

Function Declaration

Function Expressions

Calling a Function

Parameters

Pre-defined functions in JavaScript

parseInt ()

parseFloat ()

isNAN ()

isFinite ()

eval ()

Scope of Variables

SIMPLE BLOG APP

SIMPLE BLOG APP

Requirements

Setting up the environment

To Run the code

Python Boot Camp Experience!!!

INTRODUCTION

Hello world!

Happy coding

Eat, code, sleep,

Conclusion

Introduction to Python Functions!!

Built-In Functions

Creating a function

Calling a function

Arguments

Positional Arguments

Arguments and Parameters

Number of Arguments

Default Value Parameter

Return Values To let a function return a value, use the return statement: def sum(x): return 4 + x print(sum(1)) # 5 print(sum(3)) # 7 print(sum(10)) # 14

Python Basics! Python 101!

Some of python's applications include:

Getting started with python

On a mac

Your first program in python

Executing the python program

Python basic syntax

Rules for writing identifiers

Naming Global Variables

Naming Classes

Naming instance Variables

Naming modules and Package Names

Naming functions

Naming Constants

Comments

Variables and Data Types in python

Variables

Data types

Arithmetic Operators

Return Values
To let a function return a value, use the return statement:

`def sum(x): return 4 + x print(sum(1)) # 5 print(sum(3)) # 7 print(sum(10)) # 14`