Introduction to Python. An easy way to learn the Python programming language: does it exist?

Python 3 is a modern language that makes it easy and enjoyable to write programs.

To print values, Python has the print() function. Inside the parentheses, separated by commas, we write what we want to output. Here's a program that does a few calculations:

Print(5 + 10) print(3 * 7, (17 - 2) * 8) print(2 ** 16) # two asterisks mean exponentiation print(37 / 3) # one slash means division with a fraction answer print(37 // 3) # two slashes calculate the quotient of a whole division # this is like the div operation in other languages ​​print(37 % 3) # the percentage calculates the remainder of a whole division # this is like the mod operation in other languages

To enter data into the program, we use the input() function. It reads one line.

Here is a program that reads the username and greets him:

Peter print("What is your name?") name = input() # read the string and put it in the variable name print("Hello, " + name + "!")

We will write programs that read data, process it and output some result. When run on a computer, such programs read data that the user enters from the keyboard and display the result on the screen.

Let's try to write a program that reads two numbers and displays their sum. To do this, we count two numbers and store them in variables a and b, using the assignment operator =. To the left of the assignment operator in Python programs is the name of the variable - for example, a string of Latin letters. Any expression can be placed to the right of the assignment operator. The name will indicate the result of evaluating the expression. Play this program and look at the results:

5 7 a = input() b = input() s = a + b print(s)

We see that the program outputs 57, although in real life 5 + 7 would be 12. This happened because Python in the third line “added” two strings, not two numbers. In Python, two lines are added like this: the second line is added to the first line.

Note that in the visualizer, the contents of variables a and b are enclosed in quotes. This means that a and b contain strings, not numbers.

In Python, all data is called an object. The number 2 is represented by the object "number 2", the string "hello" is the object "string "hello" ".

Every object belongs to some type. Strings are stored in objects of type str , integers are stored in objects of type int , fractional numbers (real numbers) are stored in objects of type float . The type of an object determines what actions can be done with objects of that type. For example, if the variables first and second contain objects of type int , then they can be multiplied, but if they contain objects of type str , then they cannot be multiplied:

First = 5 second = 7 print(first * second) first = "5" second = "7" print(first * second)

To convert a string of numbers to an integer, we'll use the int() function. For example, int("23") will return the number 23 .

Here is an example of a correct program that reads two numbers and prints their sum:

5 7 a = int(input()) b = int(input()) s = a + b print(s)

Step-by-step instructions for anyone who wants to learn Python programming (or programming in general) but doesn't know where to take the first step.

What to do?

We looked through a lot of training materials and just good articles and compiled a list of what you need to learn in order to master this programming language and develop in it.

1. Learn the basics first. Learn what variables, control structures, data structures are. This knowledge is necessary without being tied to a specific language.

2. Study literature. Start with the classic – Dive into Python. This book can actually become a reference book. You can also read Michael Dawson “Programming in Python” and Alexey Vasiliev “Python with examples. Practical programming course." Dawson is an experienced programmer and teacher, and in the book he teaches programming by creating simple games. In Vasiliev's book, on the contrary, more attention is paid to the fundamentals and theory.

4. Take the Introduction to Computer Science and Python Programming course from MIT.

5. Find out what libraries other Pythonists use and for what purposes. Find something interesting for yourself.

6. If you are interested in web technologies, pay attention to the Flask and Django frameworks. Find out for what purposes which one is better suited, start studying the one that suits you.

7. Learn how to obtain and analyze data sets from individual sites, from around the Internet and anywhere else - just try to stay within the law.

8. Look for information about machine learning methods.

9. Optimize work with tools, automate routine and everything that is not yet automated.

Where to go?

Several useful links to resources that will help you Google a little less and decide in which direction to work.

Useful resources

Python Tutor

This tool helps you overcome a fundamental barrier to understanding the programming language you're learning: by visualizing the code, this resource provides insight into what's happening as the computer executes each line of code.

Bucky Roberts on YouTube

If you are not familiar with programming, these tutorials will help you a lot. They are easy to understand and cover everything you might need first, starting with language installation.

Derek Banas on Python on YouTube

Derek is a self-taught programmer and has his own take on the approach to learning programming languages. He makes short video reviews of various languages, 40-60 minutes long, in which he tells everything you need to generally understand the purpose of the language.

Corey Schafer on YouTube

Corey has good videos on string formatting, generators, programming terms (combinations and permutations, DRY, closures) and much more to help you understand the concepts.

Django Getting Started

Official documentation for the Django web framework. Covers everything you need to know when getting started, from setup to your first application.

Introduction to Flask

A video course on YouTube for those who want to get acquainted with Flask, understand some of its subtleties and find out why it is needed at all.

Useful links

Newbie

Python 3 for Beginners
"A Byte of Python"

Do you want to enter the world of programming and quickly write your first few programs? Or do you dream of learning new languages, but don't know where to start? Pay attention to courses on the basics of programming in Python. Next, you will learn more about why this language is recommended for beginners and what programs can be created in it.

Python Basics for Beginner Programmers

Python is a powerful, high-level, object-oriented programming language created by Guido van Rossum. It has an easy-to-use syntax, making it an ideal language for those trying to learn programming for the first time. To continue getting acquainted with the language, you can read the book by Dmitry Zlatopolsky “Python - Basics of Programming”. But we'll start with the very basics. There is a lot of literature in this area. Another option is Harry Percival’s books “Python. Test-driven development.” It talks about language from a practical point of view.

Using the language in practice

So, what is written in Python or “Python”, as it is also called among programmers, and why learn it? Python is a general purpose language. It is used to write web applications using various frameworks, system utilities and applications for automating various actions. There are now enough courses on the basics of programming in Python to try learning the language on your own.

It could become the basis of a new profession, as it has a wide range of applications from web development, scientific and mathematical computing to desktop graphical user interfaces. It is also good for prototyping. That is, a prototype is first created in Python, then the concept can be transferred to faster and compiled programming languages. Using this language, you can create desktop applications with a graphical interface and write games, for which there is a special library. The basics of algorithmization and programming in Python are suitable for creating applications for mobile devices.

Why learn Python

Python also uses a very simple and concise syntax and dynamic typing. Knowledge of the basics of algorithmization and programming in Python allows you to quickly create a program and run it. If you need a language to quickly create applications and scripts across multiple domains, you'll be hard-pressed to find a better alternative than Python. It has a number of obvious advantages over other programming languages:

• universal use - different types of applications can be written in this language, therefore, along with its mastery, wide opportunities for using this language open up;
• simplicity - the language was originally developed to simplify human work with it;
• popularity among programmers and demand in the labor market - Python is widely used in various projects;
• a large number of available libraries expand the capabilities of the language and make it even more universal;
• cross-platform - a program written once will work on any platform that has a language interpreter;
• One of the important advantages of the language is its high-quality documentation.

Python is also one of the oldest web development languages, created by Guido van Rossum at the National Research Institute for Mathematics and Computer Science in the Netherlands in the early 90s. The language borrows heavily from C++, C and other scripting languages. It uses English keywords that make up most of Python programming. If you master them, then you can consider that for the most part you have already mastered the language. This will take some time and you will need to understand the basic concepts before starting. So let's start by getting to know them.

Benefits of Python

One of the key benefits of Python programming is its interpretive nature. This means that the program code is not compiled into an executable file, but is executed by the interpreter every time it is launched by the user. Therefore, to run the program, it must be present on the computer where you will create programs. The interpreter and standard library are available in binary or source form from the Python website and can run smoothly on all major operating systems.

So, the main advantages of Python include:

Python is a great choice because it supports application development, from games to browsers to word processing.

How to install and run the interpreter

In order to start writing in Python, you need to download and install its interpreter on the official website of the language, selecting the version for your operating system. It is worth noting that there are two branches of the language - the second and third. It's better to start learning the basics of Python 3 if you haven't installed another version yet. When installing on Windows, be sure to pay attention to whether the Add Python to Path option and the Pip utility are enabled. After installation, you can run it. To do this, you need to enter: “python” in the command line, and it will start. Three angle brackets will appear in the window, indicating that you are in the interpreter. This programming language is also freely available, and you can find tips, third-party tools, programs, modules, and additional documentation.

Keywords in Python

In the interpreter, you can perform actions in the language interactively. Each action is performed immediately after pressing Enter. You can use it as an advanced calculator. But writing a large program in an interpreter is too labor-intensive. Therefore, it makes sense to use text editors. The finished text file can then be executed by the interpreter. One of the fundamentals of Python is that any blocks in it are defined by indentation, so you must indent in order to run a block and remove it. The interpreter can be easily extended with new data types or functions in C++ or C. The Python programming language works as an extension for custom applications. What makes this language so easy to learn is the fact that it uses English keywords rather than punctuation, and has fewer syntactic constructs than other programming languages.

Getting started with Python

Before you start working outside the interpreter, to create a program, you need to open a text editor and create an empty file with utf-8 encoding and set the extension to “py”. It is best to use special code editors for programmers for this purpose. The first line needs to indicate the encoding. Lines starting with a # are considered comments and are not executed. Python is implicitly and dynamically typed, so you don't need to declare variables. Types are enforced and variables are also case sensitive, so var and VAR are treated as two separate variables. If you want to know how any object works, you just need to type the following: “help(object)”. You can also use the “dir(object)” command to find out all the methods of a particular option, and you can use the “__doc__” object to find out its docstring.

How to run a written program

You must also run the written program on the command line. To do this, you need to write the name of the interpreter and, separated by a space, the name of the file with the written program. When starting the program, you must specify the full path to the file. This is not always easy, as the path can be very long, so sometimes it is easier to change the current directory on the command line and start the interpreter there. To do this, you need to go to the desired directory, hold down the shift key, right-click on the directory and select the “open command window” option in the menu that opens. Then the command line will be launched in this directory. Next, in the console window, you need to enter the name of the interpreter and, separated by a space, the name of the file that is located in it.

Language syntax

The basics of programming in Python are not too different from other languages, but variables have a slightly different meaning. Python does not have required symbols to complete statements. Any blocks are defined using indentation, so you must indent to start a block and remove it. For multiline comments, you must use multiline strings. Values ​​are assigned using the “=” sign, and equality testing is done with two of them “==”. You can decrease or increase values ​​using the = or -= operators with a sum on the right side. This can work with strings and other data types. You can also use multiple variables on one line.

Data Types in Python

Now let's look at data types. Python is based on data structures - dictionaries (dict), tuples (tuples) and lists (lists). Sets can be found in the library of sets, which are available in all versions of Python. Lists are similar to one-dimensional arrays, although you can also have lists of other lists. Dictionaries are essentially associative arrays or hash tables. Tuples are one-dimensional arrays. Now arrays in Python can be of any type, and ypes is always zero. Negative numbers start from the end to the beginning, and -1 is the last element. Variables can also point to functions.

Strings in Python

Python strings can use single or double quotes, and you can use one kind of quotation marks in a string using another kind. Multiline strings are enclosed in single or triple double quotes. To fill strings with values, you can use the modulo(%) operator followed by tuple. Each % is replaced by an element of the tuple from left to right, and you can also use dictionary substitutions. Python flow control statements: “while”, “for” and “if”. To branch you need to use “if”. To enumerate through a list, use “for”. To get a list of numbers, use a range.

Functions in Python

The keyword “def” is used to declare functions. Binding another object to a variable removes the old one and replaces the immutable types. Optional arguments can be specified in a function declaration after the required arguments, giving them default values. In the case of named arguments, the argument name is assigned a value. Functions can return a tuple, and you can efficiently return multiple values ​​using tuple unboxing. Parameters are passed by reference, but tuples, ints, strings, and other immutable types are immutable because only the memory location of the element is passed.

You have just begun your acquaintance with the language, so do not be afraid of mistakes and turn to available resources to continue learning this interesting and useful programming language.

As a well-designed programming language, Python is well suited for solving real-world problems that developers face every day. It is used in a wide range of applications - both as a tool for managing other software components and for implementing independent programs. In fact, the range of roles that Python can play as a multi-purpose programming language is practically unlimited: it can be used to implement

anything from websites and game programs to controlling robots and spaceships.

However, Python's uses today can be broken down into several broad categories. The next few sections describe the most common uses of Python today, as well as the tools used in each area. We will not have the opportunity to do research on the tools mentioned here. If any of these interest you, please visit the Python Project website for more

System programming

much more.

The Python standard library is fully compliant with POSIX standards and supports all the typical operating system tools: environment variables, files, sockets, pipes, processes, multi-threaded execution model, pattern matching using regular expressions, command line arguments, standard interfaces for accessing data streams, running shell commands, appending filenames, and more

In addition, system interfaces in Python are designed to be portable, such as the directory tree copy script, which requires no modifications no matter what operating system it is used on. The Stackless Python system used by EVE Online also offers improved parallel processing solutions.

GUI

tkinter can be used without changes in MS Windows, X Window (on UNIX and Linux systems) and Mac OS (both in the classic version and in OS X). The free PMW extension package contains additional visual components for the tkinter suite. In addition, there is the wxPython GUI API, based on the C++ library, which offers an alternative set of tools for building portable GUIs in Python.

High-level tools such as PythonCard and Dabot are built on top of APIs such as wxPython and tkinter. By choosing the appropriate library, you will also be able to use other GUI tools such as Qt (using PyQt), GTK (using PyGtk), MFC (using PyWin32), .NET (using IronPython), Swing (using Jython - the implementation of the Python language in Java, which is described in Chapter 2, or JPype). To develop web-based applications or those that do not have high UI requirements, you can use Jython, Python web frameworks, and CGI scripts, which are described in the next section and provide additional capabilities for creating a user interface.

Web scripts

emails; load web pages from specified URLs; parse HTML and XML markup of received web pages; carry out interactions using XML-RPC, SOAP and Telnet protocols and much more.

The libraries included with Python make implementing such tasks surprisingly easy.

Additionally, there is a huge collection of third-party tools for creating network programs in Python that can be found on the Internet. For example, the HTMLGen system allows you to create HTML pages based on Python class definitions. The mod_python package is designed to run Python scripts under the Apache web server and supports Python Server Pages engine templates. The Jython system provides

seamless Python/Java integration and supports server-side applets that run on the client side.

In addition, there are full-fledged web development packages for Python such as Django, TurboGears, web2py, Pylons, Zope, and WebWare that support the ability to quickly create fully functional, high-quality websites in Python. Many of them include features such as object-relational mappings, Model/View/Controller architecture, server-side scripting, template support, and AJAX technologies, providing

Complete and reliable solutions for web application development.

Component Integration

systems in C and C++ makes it a convenient and flexible language for describing the behavior of other systems and components. For example, integration with a C library allows Python to check for and run library components, and embedding Python into software products allows software products to be customized without having to rebuild the products or ship them with source code.

Tools like Swing and SIP, which automatically generate code, can automate the steps of linking compiled components in Python for later use in scripts, and the Cython system allows programmers to mix Python and C code. Huge Python platforms like support COM

in MS Windows, Jython - a Java implementation, IronPython - a .NET implementation, and various CORBA implementations provide alternative ways to organize interactions with software components. For example, on the Windows operating system, Python scripts can use application control platforms such as MS Word and Excel.

Database Applications

The standard pickle module implements a simple object storage system that allows programs to save and restore Python objects in files or specialized objects. You can also find a third-party system on the Internet called ZODB.

It is a completely object-oriented database

for use in Python scripts. There are also

tools such as SQLObject and SQLAlchemy that display

relational tables into the Python class model. Since Python 2.5,

The SQLite database has become a standard part of Python.

Rapid prototyping

leave it in Python, which will significantly simplify the maintenance and use of such a system.

Math programming

and scientific computing

Additional math tools for Python support the ability to create animation effects and 3D objects, allow you to organize parallel calculations, and so on. For example, the popular SciPy and ScientificPython extensions provide additional libraries for scientific computing and take advantage of the NumPy extension capabilities.

Games, images, artificial intelligence,

XML robots and much more

Create game programs and animation videos using

pygame systems

Exchange data with other computers via serial

port using the PySerial extension

Process images using PIL, PyOpenGL extensions,

Blender, Maya and others

Control the robot using the PyRo tool

Parse XML documents using the xml package, xmlrp- module

clib and third party extensions

Program artificial intelligence using a neuro-emulator

networks and expert system shells

Analyze natural language phrases using the NLTK package.

You can even play solitaire using PySol. Support for many other application areas can be found on the PyPI website or by using search engines (search for links using Google or http://www.python.org).

Generally speaking, many of these uses of Python are just variations of the same role called component integration. Using Python as an interface to component libraries written in C makes it possible to write Python scripts to solve problems in a wide variety of application areas. As a general-purpose, multi-purpose programming language that supports integration, Python can be used very widely.

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Python- a powerful and easy-to-learn programming language. It provides convenient high-level data structures and a simple but effective approach to object-oriented programming. Python interpreted language. To run the written programs, you must have a CPython interpreter. The python interpreter and large standard library are freely available as source and binary files for all major platforms on the official website Python http://www.python.org and may be redistributed without restrictions. In addition, the site contains distributions and links to numerous third-party modules and detailed documentation.
The language has a clear and consistent syntax, thoughtful modularity and scalability, thanks to which the source code written in Python programs are easy to read. Language developers Python adhere to a certain programming philosophy called “The Zen of Python”. Its text is output by the interpreter using the import this command:

Translated it sounds like this:

• Beautiful is better than ugly.
• Explicit is better than implicit.
• Simple is better than complex.
• Complex is better than confusing.
• Flat is better than nested.
• Sparse is better than dense.
• Readability matters.
• Special cases are not special enough to break the rules.
• At the same time, practicality is more important than perfection.
• Mistakes should never be hushed up.
• If they are not clearly hushed up.
• When faced with ambiguity, resist the temptation to guess.
• There should be one - and preferably only one - obvious way to do this.
• Although it may not be obvious at first if you are not Dutch.
• Now is better than never.
• Although never is often better than right now.
• If the implementation is difficult to explain, the idea is bad.
• If the implementation is easy to explain, the idea is probably good.
• Namespaces are a great thing! We will make more of them!

Python is an actively developing programming language, new versions are released approximately every two and a half years. Due to this and some other reasons, Python There are no ANSI, ISO or other official standards; CPython takes over.

History of the creation of the language

Development of the Python language began in the late 1980s by an employee of the Dutch CWI Institute. The Amoeba distributed OS required an extensible scripting language for which Guido van Rossum created Python. The new language borrowed some developments from the ABC language, which was focused on teaching programming. In February 1991, Guido published the source text in the alt.sources newsgroup. The name of the language does not come from the type of reptile. The author named the language after the popular 1970s British comedy TV show Monty Python's Flying Circus. However, the emblem of the language is represented by snake heads. After extensive testing, the first version of Python 3.0 was released. Today both branches of development are supported (Python 3.x and 2.x).

Python was created under the influence of many programming languages: Modula-3, C, C++, Smalltalk, Lisp, Fortran, Java, Miranda, Icon. Although Python has a fairly distinctive syntax, one of the design principles of the language is the principle of least surprise.

Standard Library

The rich standard library is one of the attractions of Python. It provides tools for working with many network protocols and Internet formats. There are modules for working with regular expressions, text encodings, multimedia formats, cryptographic protocols, and archives. In addition to the standard library, there are many libraries that provide an interface to all system calls on different platforms.
For Python, the DB-API 2 database programming interface specification has been adopted and packages corresponding to this specification have been developed for access to various DBMSs: Oracle, MySQL, PostgreSQL, Sybase, Firebird (Interbase), Informix, Microsoft SQL Server and SQLite.
The NumPy library for working with multidimensional arrays allows you to achieve scientific calculation performance comparable to specialized packages. SciPy uses NumPy and provides access to a wide range of mathematical algorithms. Numarray is specifically designed for operations with large volumes of scientific data.
Python provides a simple and convenient C API for writing your own modules in C and C++. A tool like SWIG allows you to almost automatically obtain bindings for using C/C++ libraries in Python code. The standard library tool ctypes allows Python programs to directly access dynamic libraries written in C. There are modules that allow you to embed C/C++ code directly into Python source files, creating extensions on the fly.
Python and the vast majority of libraries for it are free and supplied in source code. Moreover, unlike many open source systems, the license does not in any way restrict the use of Python in commercial development and does not impose any obligations other than copyright indications.

Areas of application

Python is a stable and widespread language. It is used in many projects and in various capacities: as a primary programming language or for creating extensions and application integrations. A large number of projects have been implemented in Python, and it is also actively used to create prototypes for future programs. Python is used by many large companies.
Python with the NumPy, SciPy and MatPlotLib packages is actively used as a universal environment for scientific calculations as a replacement for the common specialized commercial packages Matlab, IDL, etc.
Professional 3D graphics programs such as Houdini and Nuke use Python to extend the standard capabilities of the programs.

Sources

Presentations

Homework

Prepare messages:

• Python as a tool for scientists
• Python and Ruby (comparison)
• Python and WEB
• Creating windowed applications using Python and graphics libraries (wxPython, PyQt, PyGTK, etc.)