TD!

Posted on Aug 20

Day #1 (Part 1) || revisiting Python from scratch

#100daysofmiva #100daysofcode #python

print("Hello, World!")

What is Python?

Python is a popular programming language. It was created by Guido van Rossum, and released in 1991.

It is used for:

web development (server-side),
software development,
mathematics,
system scripting.

What can Python do?

Python can be used on a server to create web applications.
Python can be used alongside software to create workflows.
Python can connect to database systems. It can also read and modify files.
Python can be used to handle big data and perform complex mathematics.
Python can be used for rapid prototyping, or for production-ready software development.

Why Python?

Python works on different platforms (Windows, Mac, Linux, Raspberry Pi, etc).
Python has a simple syntax similar to the English language.
Python has syntax that allows developers to write programs with fewer lines than some other programming languages.
Python runs on an interpreter system, meaning that code can be executed as soon as it is written. This means that prototyping can be very quick.
Python can be treated in a procedural way, an object-oriented way or a functional way.

To check if you have python installed on a Windows PC, search in the start bar for Python or run the following on the Command Line (cmd.exe):

C:\\Users\\_Your Name_\>python --version

To check if you have python installed on a Linux or Mac, then on linux open the command line or on Mac open the Terminal and type:

python --version

As we learned in the previous page, Python syntax can be executed by writing directly in the Command Line:

>>> print("Hello, World!")
Hello, World!

Or by creating a python file on the server, using the .py file extension, and running it in the Command Line:

C:\Users\Your Name>python myfile.py

Creating a Comment

Comments starts with a #, and Python will ignore them:

#This is a comment
print("Hello, World!")

Creating Variables

Python has no command for declaring a variable.

A variable is created the moment you first assign a value to it.

x = 5
y = "John"
print(x)
print(y)

Variable Names

A variable can have a short name (like x and y) or a more descriptive name (age, carname, total_volume). Rules for Python variables:

A variable name must start with a letter or the underscore character
A variable name cannot start with a number
A variable name can only contain alpha-numeric characters and underscores (A-z, 0-9, and _ )
Variable names are case-sensitive (age, Age and AGE are three different variables)
A variable name cannot be any of the Python keywords.

Global Variables

x = "awesome"

def myfunc():
  print("Python is " + x)

myfunc()

x = "awesome"

def myfunc():
  x = "fantastic"
  print("Python is " + x)

myfunc()

print("Python is " + x)

x = 1    # int
y = 2.8  # float
z = 1j   # complex

#convert from int to float:
a = float(x)

#convert from float to int:
b = int(y)

#convert from int to complex:
c = complex(x)

print(a)
print(b)
print(c)

print(type(a))
print(type(b))
print(type(c))

Random Number

import random

print(random.randrange(1, 10))

_An interesting example of Slicing:
_

explain b = "Hello, World!"
print(b[-5:-2])

Variable Assignment:

python b = "Hello, World!"

This line assigns the string "Hello, World!" to the variable b.

String Slicing:

python print(b[-5:-2])

This line prints a slice of the string b. Here's how the slicing works:

Negative Indexing: In Python, negative indices count from the end of the string. So, -1 is the last character, -2 is the second last, and so on.
Slice b[-5:-2]: This means "start from the 5th character from the end and go up to (but not including) the 2nd character from the end."

Let's visualize the string with indices:

H e l l o , W o r l d ! 0 1 2 3 4 5 6 7 8 9 10 11 12 -13-12-11-10 -9 -8 -7 -6 -5 -4 -3 -2 -1

So, b[-5:-2] corresponds to the characters orl from the string "Hello, World!".

Therefore, the output of print(b[-5:-2]) will be:

orl

Python Strings