Python is a wonderful and powerful programming language that's easy to use (easy to read and write) and, with Raspberry Pi, lets you connect your project to the real world.
Also, how to install packages for Python 3.9? When I do pip3 install, the package gets installed for Python 3.7. (In case you're wondering why I want 3.9, it's because 3.7 has a bug in subprocess.run that causes Python to hang if the subprocess never returns - the timeout doesn't work. This has been fixed in Python. Online Python Compiler, Online Python Editor, Online Python IDE, Python Coding Online, Practice Python Online, Execute Python Online, Compile Python Online, Run Python Online, Online Python Interpreter, Execute Python Online (Python v2.7.13). Thonny is a new Python IDE for learning and teaching programming that can make program visualization a natural part of the beginners' workflow. Among its prominent features are different ways of stepping through the code, step-by-step expression evaluation, intuitive visualization of the call stack and mode for explaining the concepts of references and heap. Stack Exchange network consists of 176 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Learn the Python programming language or use the program as a training manual to explain the concepts of Python to your students. Write code using simple commands or complex operations. Work with syntax highlighting, code completion, and debugging tools. Thonny 3.3.6 is free to download from our software library. The size of the latest installation package available is 16.7 MB.
Python syntax is very clean, with an emphasis on readability, and uses standard English keywords.
Thonny
The easiest introduction to Python is through Thonny, a Python3 development environment. Open Thonny from the Desktop or applications menu:
Thonny gives you a REPL (Read-Evaluate-Print-Loop), which is a prompt you can enter Python commands into. Because it's a REPL, you even get the output of commands printed to the screen without using print. In the Thonny application, this is called the Shell window.
You can use variables if you need to but you can even use it like a calculator. For example:
Thonny also has syntax highlighting built in and some support for autocompletion. You can look back on the history of the commands you've entered in the REPL with Alt + P (previous) and Alt + N Amazon gaming app. (next).
Basic Python usage
Hello world in Python:
Simple as that!
Indentation
Some languages use curly braces { and } to wrap around lines of code which belong together, and leave it to the writer to indent these lines to appear visually nested. However, Python does not use curly braces but instead requires indentation for nesting. For example a for loop in Python:
The indentation is necessary here. A second line indented would be a part of the loop, and a second line not indented would be outside of the loop. For example:
would print:
whereas the following:
Free IP Camera Software. Easy to use MJPEG, MPEG-4, H.264, RTSP, RTMP viewer & recorder. Easy connection of 400+ brands. Clean Intuitive interface. Ip camera viewer software free. Netcam Studio is a free IP security camera software that can be used for home. View any IP Camera on TV or Monitor Configurable camera sequences and quad views HDMI and Composite Video Output NetcamViewer Software enables you to display images of network cameras in a way that, until now, was not available to everyone. We develop both customer-specific applications and commercial software. HTTP://192.168.1.101 represents the IP address of the camera being accessed. Find your camera's IP address. If you don't know its IP address, click here. Open a web browser and type the IP address. Enter your login information. Go to SETTING BASIC Network Information to find the HTTP port number used by the camera. The default is 80.
would print:
Variables
To save a value to a variable, assign it like so:
Note that data types were not specified with these variables, as types are inferred, and can be changed later.
This time I used comments beside the increment command.
Comments
Comments are ignored in the program but there for you to leave notes, and are denoted by the hash # symbol. Multi-line comments use triple quotes like so:
Lists
Python also has lists (called arrays in some languages) which are collections of data of any type:
Lists are denoted by the use of square brackets [] and each item is separated by a comma.
Iteration
Some data types are iterable, which means you can loop over the values they contain. For example a list:
This takes each item in the list numbers and prints out the item:
Note I used the word number to denote each item. This is merely the word I chose for this - it's recommended you choose descriptive words for variables - using plurals for lists, and singular for each item makes sense. It makes it easier to understand when reading.
Other data types are iterable, for example the string:
This loops over each character and prints them out:
Range
The integer data type is not iterable and trying to iterate over it will produce an error. For example:
will produce:
However you can make an iterable object using the range function:
range(5) contains the numbers 0, 1, 2, 3 and 4 (five numbers in total). To get the numbers 1 to 5 (inclusive) use range(1, 6).
Length
You can use functions like len to find the length of a string or a list:
If statements
You can use if statements for control flow:
Python files in Thonny
To create a Python file in Thonny, click File > New and you'll be given a window. This is an empty file, not a Python prompt. You write a Python file in this window, save it, then run it and you'll see the output in the other window.
For example, in the new window, type:
Then save this file (File > Save or Ctrl + S) and run (Run > Run Module or hit F5) and you'll see the output in your original Python window.
Executing Python files from the command line
You can write a Python file in a standard editor, and run it as a Python script from the command line. Just navigate to the directory the file is saved in (use cd and ls for guidance) and run with python3, e.g. python3 hello.py.
Other ways of using Python
Command Line
The standard built-in Python shell is accessed by typing python3 in the terminal.
This shell is a prompt ready for Python commands to be entered. You can use this in the same way as Thonny, but it does not have syntax highlighting or autocompletion. You can look back on the history of the commands you've entered in the REPL by using the Up/Down keys. Use Ctrl + D to exit.
IPython
IPython is an interactive Python shell with syntax highlighting, autocompletion, pretty printing, built-in documentation, and more. IPython is not installed by default. Install with:
Then run with ipython from the command line. It works like the standard python3, but has more features. Try typing len? and hitting Enter. You're shown information including the docstring for the len function:
Try the following dictionary comprehension:
Thonny Org
This will pretty print the following:
In the standard Python shell, this would have printed on one line:
You can look back on the history of the commands you've entered in the REPL by using the Up/Down keys like in python. The history also persists to the next session, so you can exit ipython and return (or switch between v2/3) and the history remains. Use Ctrl + D to exit.
Installing Python libraries
apt
Some Python packages can be found in the Raspberry Pi OS archives, and can be installed using apt, for example:
This is a preferable method of installing, as it means that the modules you install can be kept up to date easily with the usual sudo apt update and sudo apt full-upgrade commands.
pip
Not all Python packages are available in the Raspberry Pi OS archives, and those that are can sometimes be out of date. If you can't find a suitable version in the Raspberry Pi OS archives, you can install packages from the Python Package Index (known as PyPI).
To do so, install pip:
Online Thonny Python Compiler
Then install Python packages (e.g. simplejson) with pip3:
Read more on installing software in Python here.
piwheels
Python syntax is very clean, with an emphasis on readability, and uses standard English keywords.
Thonny
The easiest introduction to Python is through Thonny, a Python3 development environment. Open Thonny from the Desktop or applications menu:
Thonny gives you a REPL (Read-Evaluate-Print-Loop), which is a prompt you can enter Python commands into. Because it's a REPL, you even get the output of commands printed to the screen without using print. In the Thonny application, this is called the Shell window.
You can use variables if you need to but you can even use it like a calculator. For example:
Thonny also has syntax highlighting built in and some support for autocompletion. You can look back on the history of the commands you've entered in the REPL with Alt + P (previous) and Alt + N Amazon gaming app. (next).
Basic Python usage
Hello world in Python:
Simple as that!
Indentation
Some languages use curly braces { and } to wrap around lines of code which belong together, and leave it to the writer to indent these lines to appear visually nested. However, Python does not use curly braces but instead requires indentation for nesting. For example a for loop in Python:
The indentation is necessary here. A second line indented would be a part of the loop, and a second line not indented would be outside of the loop. For example:
would print:
whereas the following:
Free IP Camera Software. Easy to use MJPEG, MPEG-4, H.264, RTSP, RTMP viewer & recorder. Easy connection of 400+ brands. Clean Intuitive interface. Ip camera viewer software free. Netcam Studio is a free IP security camera software that can be used for home. View any IP Camera on TV or Monitor Configurable camera sequences and quad views HDMI and Composite Video Output NetcamViewer Software enables you to display images of network cameras in a way that, until now, was not available to everyone. We develop both customer-specific applications and commercial software. HTTP://192.168.1.101 represents the IP address of the camera being accessed. Find your camera's IP address. If you don't know its IP address, click here. Open a web browser and type the IP address. Enter your login information. Go to SETTING BASIC Network Information to find the HTTP port number used by the camera. The default is 80.
would print:
Variables
To save a value to a variable, assign it like so:
Note that data types were not specified with these variables, as types are inferred, and can be changed later.
This time I used comments beside the increment command.
Comments
Comments are ignored in the program but there for you to leave notes, and are denoted by the hash # symbol. Multi-line comments use triple quotes like so:
Lists
Python also has lists (called arrays in some languages) which are collections of data of any type:
Lists are denoted by the use of square brackets [] and each item is separated by a comma.
Iteration
Some data types are iterable, which means you can loop over the values they contain. For example a list:
This takes each item in the list numbers and prints out the item:
Note I used the word number to denote each item. This is merely the word I chose for this - it's recommended you choose descriptive words for variables - using plurals for lists, and singular for each item makes sense. It makes it easier to understand when reading.
Other data types are iterable, for example the string:
This loops over each character and prints them out:
Range
The integer data type is not iterable and trying to iterate over it will produce an error. For example:
will produce:
However you can make an iterable object using the range function:
range(5) contains the numbers 0, 1, 2, 3 and 4 (five numbers in total). To get the numbers 1 to 5 (inclusive) use range(1, 6).
Length
You can use functions like len to find the length of a string or a list:
If statements
You can use if statements for control flow:
Python files in Thonny
To create a Python file in Thonny, click File > New and you'll be given a window. This is an empty file, not a Python prompt. You write a Python file in this window, save it, then run it and you'll see the output in the other window.
For example, in the new window, type:
Then save this file (File > Save or Ctrl + S) and run (Run > Run Module or hit F5) and you'll see the output in your original Python window.
Executing Python files from the command line
You can write a Python file in a standard editor, and run it as a Python script from the command line. Just navigate to the directory the file is saved in (use cd and ls for guidance) and run with python3, e.g. python3 hello.py.
Other ways of using Python
Command Line
The standard built-in Python shell is accessed by typing python3 in the terminal.
This shell is a prompt ready for Python commands to be entered. You can use this in the same way as Thonny, but it does not have syntax highlighting or autocompletion. You can look back on the history of the commands you've entered in the REPL by using the Up/Down keys. Use Ctrl + D to exit.
IPython
IPython is an interactive Python shell with syntax highlighting, autocompletion, pretty printing, built-in documentation, and more. IPython is not installed by default. Install with:
Then run with ipython from the command line. It works like the standard python3, but has more features. Try typing len? and hitting Enter. You're shown information including the docstring for the len function:
Try the following dictionary comprehension:
Thonny Org
This will pretty print the following:
In the standard Python shell, this would have printed on one line:
You can look back on the history of the commands you've entered in the REPL by using the Up/Down keys like in python. The history also persists to the next session, so you can exit ipython and return (or switch between v2/3) and the history remains. Use Ctrl + D to exit.
Installing Python libraries
apt
Some Python packages can be found in the Raspberry Pi OS archives, and can be installed using apt, for example:
This is a preferable method of installing, as it means that the modules you install can be kept up to date easily with the usual sudo apt update and sudo apt full-upgrade commands.
pip
Not all Python packages are available in the Raspberry Pi OS archives, and those that are can sometimes be out of date. If you can't find a suitable version in the Raspberry Pi OS archives, you can install packages from the Python Package Index (known as PyPI).
To do so, install pip:
Online Thonny Python Compiler
Then install Python packages (e.g. simplejson) with pip3:
Read more on installing software in Python here.
piwheels
The official Python Package Index (PyPI) hosts files uploaded by package maintainers. Some packages require compilation (compiling C/C++ or similar code) in order to install them, which can be a time-consuming task, particlarly on the single-core Raspberry Pi 1 or Pi Zero.
Python Thonny Online Editor
piwheels is a service providing pre-compiled packages (called Python wheels) ready for use on the Raspberry Pi. Raspberry Pi OS is pre-configured to use piwheels for pip. Read more about the piwheels project at www.piwheels.org.
Python Thonny Online Course
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