For list Python

da Cristina | Mag 29, 2021 | Python

In this lesson I will do some examples of using the for loop with the list element in Python.

For list Python – Print a list in reverse order using the for loop

This problem can have several solutions, we will analyze some of them.

The first solution makes use of the reversed() function, to invert a list, the second one uses the length of the list, the len() function.

Let’s start by analyzing the first solution in detail.

First we create a list of elements: numbers = [1, 2, 3, 4, 5], then we use the existing function reversed() to reverse the elements of a list. So we print the inverted elements using the for loop in Python on the list.

Here is a possible solution:

numbers = [1, 2, 3, 4, 5]
numbers_reversed = reversed(numbers)
for number in numbers_reversed:
    print(number)

Let’s now work out a second solution, calculating the length of the list from which we will subtract one. In this way we find the index of the last element of the list. Then we will use the appropriate for loop.

Here is the complete code of the second solution to our algorithm that uses the for on lists in Python:

numbers = [1, 2, 3, 4, 5]
n_numbers = len(numbers) - 1
for i in range (n_numbers, -1, -1):
    print(numbers[i])

For list Python – Compute the cube of all elements of a list

Let’s create a list of integers. With the for loop we calculate the cube of each element and print the list. We use the len function to determine the length of the list. Finally we cycle through the modified list to print the elements.

numbers = [1, 2, 3, 4, 5]

for i in range(len(numbers)):
    numbers[i] = numbers[i] * numbers[i] * numbers[i]

for number in numbers:
    print(number)

A second solution involves simply using the function in Python to calculate the powers of a number, the pow() function.

In our case we will need to raise to the cube. Then we cycle through the list with the for loop in Python.

Here is the complete sample code:

numbers = [1, 2, 3, 4, 5]

for i in range(len(numbers)):
    numbers[i] = pow(numbers[i],3)

for number in numbers:
    print(number)

These are just some simple examples of using the for loop with lists in Python, in the next lessons we will develop many other examples.

Useful links

Tutorial Python

Python Compiler

da Cristina | Mag 29, 2021 | Python

Integrate a Python Compiler Online to test the code directly.

Below you will find the basic version, scrolling the page you will find the compiler with the integration of some fundamental libraries for automatic calculation.

Basic version of the Python Compiler Online:

Write Python code using one of the most popular built-in compilers.

Python Compiler Online with Libreries

We can also use libraries like NumPy, Pandas, Matplotlib, Seaborn. Here is an advanced version of the Python Compiler with an example on the logarithmic scale:

About Python

Python is a very popular programming language created by Guido van Rossum. It was released in 1991 and has been increasingly adopted in a variety of fields since then.

Python, in fact, is a generic and high-level programming language widely used both for Web development and for the field of data science and machine learning. So it allows you to create mobile apps using cutting-edge frameworks such as Flask and Diango, and on the other hand it allows you to use libraries such as NumPy, Pandas, Matplot, Seaborn, etc …So we can say that sit is suitable both in the field of web development and in the analysis of data and automatic access.

Simple examples – Python Compiler Online:

Try some simple examples in the Python Compiler to test the programs.

First example:

Write a Python program using Pandas to create and display a one-dimensional array-like object containing an array of data.

Solution:

import pandas as pd 
ds = pd.Series([1, 3, 5, 7, 9]) 
print(ds)

Second example:

Generate a sequence of numbers from x to y excluding y, in increments of 1.

x = 1
y = 15
for a in range(x,y):
    print(a)

Third example to try in the Python online compiler:

Make a Python program that returns the total of odd and even numbers of series of numbers.

numbers = [11, 6, 9, 40, 5, 14]
count_odd = 0
count_even = 0
for x in numbers:
    if x % 2:
      count_odd += 1
    else:
      count_even += 1
print("Count even numbers :", count_even)
print("Count odd numbers :", count_odd)

Useful links

Python tutorial

1 – Introduzione al linguaggio Python

2 – Le variabili

3 – Operatori aritmetici e di assegnazione

4 – Stringhe

5 – Casting

6 – Input e print

7 – Primi esercizi in Python

8 – Errori in Python

9 – Script Python

10 – Scambio di variabili

11 – Modulo math

Install Python

da Cristina | Mag 28, 2021 | Python

Install Python is very simple and we will see it in detail on all systems. But before installation let’s make a brief introduction to this amazing programming language

Python is a language that adapts to multiple fields, such as websites, computer science, and artificial intelligence. During this tutorial we will therefore explore the various areas of expertise.

In this lesson we will see how to install Python. First let’s make a brief introduction of this fantastic programming language.

It is a language that supports object-oriented programming and is being addressed more and more, even in universities.

There are numerous frameworks developed for Python and often represent optimal solutions for quickly building applications. Among these we will deal with Flask and Django, two important open-source web frameworks, useful for creating simple internet and e-commerce sites.

I will also mention Plone, a CMS (Content Management System) used to manage a website with ease.

This last part will therefore be useful for those who want to work with these tools.

How to install Python?

To install, go to the official website: https://www.python.org/downloads/ and download the version suitable for your operating system.

Windows

First we show the installation of Python in a Windows environment.

As soon as the installation starts, you will be asked for some options, make sure you select the Add Python 3.X to PATH item.

But, if you forget to do so, don’t worry, you can still change this option by going to: control panel -> system-> advanced system settings -> environment variable.

As well as from the pictures shown below.

Then click on the edit button and add the path specifying the appropriate path.

Alternatively, you can launch the executable again, click on modify and add the check mark on Add Python to environment variables.

The Python installation is complete

Working in interactive mode

After installing Python on your PC, you can start working in interactive mode or creating scripts that can then be executed.

The interactive mode allows you to interact directly with the interpreter, this is only convenient at the beginning to learn how to do some small tests.

To work in this mode, you need to start the IDLE. IDLE is software that allows both to work interactively and to create scripts.

Starting it, the interactive interpreter will be presented with the cursor positioned after the symbol: >>> (triple major sign), the Python shell.

You can consult information about the language specifications by entering the help() command.

After entering the help, you can request, for example, information on the individual instructions of the language.

Then try to request the if statement, you will see information on the use of this statement.

To exit the help you need to type quit.

You can also avoid entering the help by typing, after the >>> symbol, the word help followed by the required term inserted in quotes inside the round brackets.

For example help (‘if’).

Well in this guide we have seen the installation of Python, in the next tutorial we will start creating our first Python program.

Useful links

Python tutorial

1 – Introduzione al linguaggio Python