Chapter 1 Introduction to Python Programming

Chapter 1 Introduction to Python Programming

Zhou [email protected]

North China Electric Power UniversityControl & Computer Engineering School

Zhou Rong

Control & Computer Engineering School

North China Electric Power University

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Outline

1.1 Computer & Programming language

1.2 Introduction to Python

1.3 Python language version and development

environment

1.4 Develop and run Python programs

1.5 Packaging and distribution of programs

1.6 Online help and related resources

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North China Electric Power University1.1 Computer & Programming language

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History of computer

n What is computer：

¨ An electronic device that can store programs

and data, execute programs automatically, and

process various digital information quickly and

efficiently.

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History of computer

n Father of computer：

¨ Alan Mathison Turing : Can Machines Think?

¨ John von Neumann pioneered game theory and,

along with Alan Turing and Claude Shannon, was

one of the conceptual inventors of the stored-

program digital computer

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History of computer

n Stored-program computer, a computer that

stores instructions in binary-number format in

its memory to enable it to perform a variety of

tasks in sequence or intermittently. The idea was

introduced in the late 1940s by John von

Neumann

EDVAC

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5 Units

n Arithmetic unit: Responsible for completing all arithmetic operations and logical operations tasks

n Control unit: Control the work of all parts of the entire computer. The controller controls all the actions of the computer hardware system.

n Memory unit: stores instructions in binary-number format ¨ 8 bits is called a byte , each byte has a unique

address§ 1KB=1024B=210

§ 1MB=1024KB=220

§ 1GB=1024MB=230 § 1TB=1024GB=240

§ 1PB=1024TB=250

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5 Units

n Input device: to accept user input (Raw data and programs )

n Output device: to convert the calculation results into a form acceptable to people and output to the corresponding medium (for example: monitor).

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Memory

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Adress Data

Bit

Byte

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Computer systemn A computer system consists of hardware and software

¨ Physical computers and peripherals are collectively referred to as hardware

¨ The programs that computers execute are part of software(=program + data + documents)

n Software is generally divided into two categories: system software and application software

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user userApplication SoftwareSystem Software

operating system

computer

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Programming Language

n A programming language, is a set of grammatical rules used to define computer programs. Each language has a unique set of syntax and program instructions

n Programming languages are divided into low-level languages and high-level languages¨ Low-level languages are machine-specific¨High-level languages are machine independent

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n Machine language and assembly language are low-level languages

n Machine language is the first generation of programming language, using binary code to write programs, readability is poor, but can be directly recognized and executed by computers

n Assembly language is a second generation programming language that uses simple mnemonics to express instructions

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Machine language program0 0 1 0 0 0 1 11 1 1 0 1 1 0 10 1 1 0 0 0 0 10 1 1 1 0 1 1 0

assembly language program

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n A high-level language is a language independent of computer architecture. Its biggest feature is that it describes the process of problem processing in a form similar to natural language ¨C、C++、C#、Java and Python

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Classification of Programming Languages

n Procedural oriented programming language¨FORTRAN、COBOL、Basic、Ada、Pascal、

Cn Object-oriented programming language¨Java、C#、C++、Smalltalk、Visual Basic

n Functional programming languages ¨Lisp、Scheme、Haskell、F#

n Logical programming language ：Prologn Python is a multiparadigm programming

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Computational Thinking and Programming Methods

n In the process of understanding and transforming the world, human beings have formed the following three basic thinking ¨ Logical thinking: characterized by reasoning and

deduction, represented by mathematics ¨ Experimental thinking: characterized by

experiment and verification, represented by physics

¨ Computational thinking: characterized by design and construction, represented by computer science

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The essence of computational thinking

n The essence of computational thinking is abstraction and automation

n Program design method belongs to the category of computational thinking, common program design method mainly includes two kinds ¨ Structured programming and object-oriented

programming ¨ Structured programming usually adopts the top-

down, stepwise refinement method of programming

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The basic idea of top-down programming

n Problem decomposition, algorithm implementation, combination program

n A program designed from the top-down method is generally implemented through the bottom-up method ¨ Implementing, running, and testing each of the

basic functions, and then testing the overall function that consists of the basic functions, can help locate errors

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Source file

n After you write a program in a text editor, save the file. The file that contains the program code is called source file.

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Program Execution

n There are two ways to convert a source file into a machine language

¨ Compiler: The Compiler translates source code into the target language

¨ Explanation: The interpreter interprets and executes high-level programming languages directly

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Classify High-Level Programming Languages by Their Execution Mechanismn Static languages and scripting languages

¨ The language executed in a compiled manner is a static language, such as C, C++, C#, Java,etc.

¨ Advantage : the compiled object code can be run directly; The object code produced by compilation is usually faster to execute

n The language executed in an interpreted manner are scripting languages, such as JavaScript, PHP, Python,etc. ¨ Advantage : the source code can be run in any

operating system interpreter, portability; Interpretative execution requires the preservation of source code, so program error correction and maintenance are very convenient 21

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North China Electric Power University1.2 Introduction to Python

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About Python

n Life is short, you need Python

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Welcome to Python -the world’s most popularn Welcome to Python—one of the world’s most widely

used computer programming languages and, according to the Popularity of Programming Languages (PYPL) Index, the world’s most popular

n https://pypl.github.io/PYPL.html

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Pythonn Is an interpreted, object - oriented programming

languagen Is an open source language with a large number of

libraries that allow you to efficiently develop a variety of applications

n Python language features¨ Simple, advanced, object oriented, extensible, free

open source, portability, rich library, embeddable n The scope of Python

Öperating system management, scientific computing （NumPy, SciPy, Pandas, SymPy, Matplotlib, OpenCV, VTK, ITK）,Web applications（Django、Flask、Pyramid, etc）,GUI, development（Tkinter、wxPython or PyQt libraries）、others (game development, etc.) 25

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1.3 Python Language Version and Development Environment

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n Two major releases: Python 2 and Python 3n Python 3 was not designed with backward

compatibility in mind n Python language implementation: The Python

interpreter n Common Python implementations:

¨ Cpython, Jython, IronPython, PyPyn An integrated development environment for Python

¨ IDLE（built-in）, Spyder, PyCharm, Eclipse + Pydevbuilt-in, Visual Studio + Python Tools for Visual Studio, PythonWin

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Let’s Do it

n Our IDE (Integrated Development Environment)

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Install anaconda

n We use the easy-to-install Anaconda Python distribution. It comes with almost everything you’ll need to work with our examples, including:¨ the IPython interpreter,¨most of the Python and data science libraries we

use,¨ a local Jupyter Notebooks server so you can load

and execute our notebooks, and¨ various other software packages, such as the

Spyder Integrated Development Environment (IDE)—we use only IPython and Jupyter Notebooks in this book.

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n Download the Python 3.x Anaconda installer for Windows, macOS or Linux from:n https://www.anaconda.com/download/

n When the download completes, run the installer and follow the onscreen instructions.

n To ensure that Anaconda runs correctly, do not move its files after you install it.

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North China Electric Power University1.4 Develop and Run Python Programs

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n There are generally two ways to develop and run Python programs ¨ Interactive mode: In command line window, type

“ipython”, press Enter,open ipython interpret, then enter small bits of Python code called snippets and immediately see their results.

¨ Interactivity is generally useful for debugging small amounts of code(snippets)

¨ Script mode: To write Python programs and save them in one or more source files(has the .py extension), which are then compiled and executed by the Python interpreter. This mode is suitable for the development of more complex applications

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Interpret and Execute Python Programs n Interactive Example(open the Anaconda Command Prompt)

Öutput Hello world!¨ Use the Python interpreter for mathematical

operations >>> 1.1+2.2+3.3+4.4+5.5 #output：16.5>>> (1+0.01)**365

¨ running multiple expressions at the same time: running multiple expressions separated by commas at the same time returns tuples >>> 2,2**10 #output：(2, 1024)

¨ Close the iPython interpreter Ctrl+d ；Or enter exit + Entercommand；Or close the command line window 33

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Interpret and Execute Python Programs n File format Example

Öutput ‘Good!’ 5 times print('Good!'*5)

¨ execute multiple lines of code(print numbers in the range of 0 to 9, with a space as the separator) for x in range(10): print(x, end=' ')

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Write and Execute Python Source File Programsn Write Python programs as text files（ .py ）n The process of writing Python source code files and

executing the program through the Python compiler/interpreter

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with extension:“.pyc”

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n Example : get your today’s lucky numberimport random # Import library modules print("Hello, world") #output：Hello, Worldprint("Your lucky random number today is：", random.choice(range(10))) #output a number randomly selected from 0 to 9 input() #wait for user input

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Executing a Python Program Using the IPython Interpreter- Law of large numbersn execute a script named RollDieDynamic.py(simulates

rolling a six-sided die, It presents a colorful animated visualization that dynamically graphs the frequencies of each die face)

n Changing to Examples Foldern Executing the Script: ipython RollDieDynamic.py 6000

1(The numbers 6000 and 1 tell this script the number of times to roll dice and how many dice to roll each time)

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Problems That May Occur at Execution Time

n Programs often do not work on the first try. For example, an executing program might try to divide by zero (an illegal operation in Python). This would cause the program to display an error message. If this occurred in a script, you’d return to the editor, make the necessary corrections and re-execute the script to determine whether the corrections fixed the problem(s).

n they’re called runtime errors or execution-time errors. Fatal runtime errors cause programs to terminate immediately without having successfully performed their jobs. Non-fatal runtime errors allow programs to run to completion, often producing incorrect results

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Writing and Executing Code in a Jupyter Notebook

n Jupyter Notebook—an interactive, browserbased environment in which you can write and execute code and intermix the code with text, images and video.

n Jupyter Notebook is similar to working with IPython—in fact,Jupyter Notebooks use IPython by default

n Point your fold as Jupyter notebook default fold:¨ Find out file named“jupyter_notebook_config.py”

by command “jupyter notebook –-generate-config”¨ add “c.NotebookApp.notebook_dir = ‘you fold path’”

in file “jupyter_notebook_config.py”

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JupyterLab interface

n enables you to manage your notebook files and other files that your notebooks use (like images and videos)

n JupyterLab also makes it convenient to write code, execute it, see the results, modify the code and execute it again.

n Open Jupyter lab in Browser¨ Anaconda Command Prompt-type in

command:jupyter lab¨ reopen JupyterLab by entering the following

address in your web browser: http://localhost:8888/lab

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n Creating a New Jupyter Notebookn Renaming the Notebook

n To the cell’s left, the notation [ ]: is where the Jupyter Notebook will display the cell’s snippet number after you execute the cell

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n To execute the current cell’s code, type Ctrl + Enter (or control + Enter).

n JupyterLab executes the code in IPython, then displays the results below the cell:

n Adding and Executing Another Cell(Shift + Enter)n Jupyter notebook enables you to work through them

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Closing JupyterLab

n When you’re done with JupyterLab, you can close its browser tab, then in the Terminal, shell or Anaconda Command Prompt from which you launched JupyterLab, type Ctrl + c (or control + c) twice.

n Jupyter team’s introduction to JupyterLab at:https://jupyterlab.readthedocs.io/en/stable/index.html

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North China Electric Power University1.5 Package and Release Programs

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n The process of packaging Python source code into executable files to run Python programs directly on operating systems where the Python interpreter is not installed is called "program distribution."

n The most common way to package and release Python programs is the third-party extension package PyInstaller

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n Install the PyInstaller package： pip install pyinstaller¨ Generating executable programs with PyInstaller:

PyInstaller option Python source file ¨ PyInstaller supports the following common options

n -h or--help：view help informationn -F or--onefile：generates a single executable file n -D or--onedir：generates a directory containing

the executable file and associated supporting files and subdirectories

n --clean：cleans the PyInstaller cache and removes temporary files from the packaging and publishing process

n Use PyInstaller to generate an executable file: pyinstaller -F hello2.py

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North China Electric Power University1.6 Online Help and Related Resources

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n Python interactive help system¨ Enter the interactive help system by typing the help()

function directly ¨ Type Help (object) to get help information about the

object¨ Example of using the Interactive Help system in

Python （1）Enter the interactive help system. Type help() and press Enter（2）Display all installed modules. Type modules and press Enter（3）Display modules related to Random. Type modules random and press Enter（4）Display the help information of module Random. Type random and press Enter（5）Display information about the random function of the Random module. Type random.random and press Enter

（6）Exit the help system. Type quit and press Enter50

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n Python interactive help system¨ Use Python's built-in functions to get help

information （1） View the list of Python built-in objects. Enter the command： >>> dir(__builtins__)（2）View the information about float. Enter the command >>> float （3）See the help information for the built-in class float

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Online Help and Related Resources

n PYTHON DOCUMENTATIONn The Python Language Reference:

¨ https://docs.python.org/3/reference/index.htmln The Python Standard Library:

¨ https://docs.python.org/3/library/index.htmln Python documentation list:

¨ https://docs.python.org/3/

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GETTING YOUR QUESTIONS ANSWERED

n Popular Python and general programming online forums include:

n pythonforum.ion https://www.dreamincode.net/forums/forum/29pyth

on/n StackOverflow.com

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GETTING JUPYTER HELPn Jupyter Notebooks support is provided through:

¨ Project Jupyter Google Group:n https://groups.google.com/forum/#!forum/jupyter

¨ Jupyter realtime chat room:n https://gitter.im/jupyter/jupyter

¨ GitHubn https://github.com/jupyter/help

¨ StackOverflow:n https://stackoverflow.com/questions/tagged/jupyter

¨ Jupyter for Education Google Group (for instructors teaching with Jupyter):n https://groups.google.com/forum/#!forum/jupyter-

education 54

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wrap up

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Documents

Chapter 1 Introduction to Python Programming