python Command in Linux
The python command in Linux runs the Python scripts or starts the Python interactive shell. Python is a high-level, interpreted programming language known for its simplicity and readability. It supports multiple paradigms, including procedural, object-oriented, and functional programming. It is widely used in Linux for scripting, automation, system administration, and software development.
Table of Contents
Here is a comprehensive guide to the options available with the python command −
Syntax of python Command
The syntax of using the python command in Linux is as follows −
python [options] [script] [arguments]
The above syntax is for systems where Python 2 is installed by default.
Or −
python3 [options] [script] [arguments]
The above syntax is for systems where Python 3 is installed by default. Since Python 2 is deprecated, most modern Linux distributions use Python 3.
In the above syntax, the [options] field is used to specify flags like -c, -m, or -V. The [script] field is used to specify the Python script to execute. The [arguments] are additional arguments passed to the script.
python Command Options
The options used with the Linux python command are listed below −
| Flag | Option | Description |
|---|---|---|
| -B | Do not write .pyc files on import. | |
| -b | Warn about str(bytes_instance), str(bytearray_instance), and invalid comparisons (-bb makes them errors). | |
| -c command | Execute a command string and exit. | |
| --check-hash-based-pycs mode | Configure hash-based .pyc file validation. | |
| -d | Enable parser debugging output (for experts). | |
| -E | Ignore Python environment variables (PYTHONPATH, PYTHONHOME). | |
| -h, -? | --help | Show Python usage and exit. |
| --help-env | Show help for Python environment variables. | |
| --help-xoptions | Show help for -X options. | |
| --help-all | Show full usage information. | |
| -i | Enter interactive mode after script execution. | |
| -I | Run in isolated mode, ignoring environment variables and user site-packages. | |
| -m module-name | Run a module as a script. | |
| -O | Remove assert statements and optimize .pyc filenames (.opt-1). | |
| -OO | Like -O, but also remove docstrings (.opt-2). | |
| -P | Prevent adding unsafe paths (example: current directory) to sys.path. | |
| -q | Suppress version and copyright messages. | |
| -s | Prevent adding the user site directory to sys.path. | |
| -S | Disable automatic import of site module. | |
| -u | Unbuffer stdout and stderr. | |
| -v | Print module import details (-vv for more). | |
| -V | --version | Show Python version (-VV for more details). |
| -W argument | Control warnings (-Wignore, -Werror, and others). | |
| -X option | Set implementation-specific options (Example: -X faulthandler). | |
| -x | Skip the first line of a script (DOS-specific). |
Examples of python Command in Linux
This section explores how to use the python command in Linux with examples −
Note − Since Python 3 is the default in modern Linux, the python3 command is used in examples.
- Running a Python Script File
- Running Python Code
- Enabling Interactive Mode
- Running a Module
- Ignoring All Environment Variables
- Enabling Debug Mode
- Enabling Isolated Mode
- Running a Python Script without Creating a Compiled File
- Controlling Warnings
- Displaying the Imported Modules
- Displaying Help for Python Environment Variables
- Displaying Usage Help
Running a Python Script File
To run a Python script file, use the python command in the following way −
python3 script.py
Running Python Code
To run the Python code strings directly from the command line, use the -c option −
python3 -c 'print("Hello, Tutorialspoint!")'
Enabling Interactive Mode
To enable the interactive mode, use the -i option with the python command −
python3 -i
A list of various Python operations in the interactive mode is given below:
Running a Python script −
print("Hello, Tutorialspoint!")
Performing a calculation −
8+4
Defining variables and performing an operation −
a=5 b=8 a+b
Creating and running a Python function −
def greet(name): return "Welcome! "+name
To exit the interactive mode, type exit() and press Enter or simply press the CTRL+D buttons.
Running a Module
Python provides various built-in modules that can be run using the -m option. For example, to run the built-in debugger, use the python command in the following manner −
python3 -m pdb script.py
Similarly, to inspect a module, use −
python3 -m pydoc math
Ignoring All Environment Variables
To ignore all the environment variables before executing a script, use the -E option. It changes the way Python script is executed.
python3 -E script.py
This ensures the script runs with Python's default settings, ignoring any modifications from the environment.
Enabling Debug Mode
To run a Python script in debug mode, use the -d option. It enables parser debugging output.
python3 -d script.py
It is only useful for experts and requires a Python build compiled with debugging support.
Enabling Isolated Mode
The isolated mode restricts access to user-specific configurations and environment variables to run scripts in a secure environment.
To run a Python script in the isolated mode, use the -I option with the python command.
python3 -I script.py
Running a Python Script without Creating a Compiled File
A .pyc file is a compiled Python bytecode file that is automatically created when a Python script is run or imported. To run the Python script without creating this file, use the -B option −
python3 -B script.py
Controlling Warnings
To control warnings while running the Python script, use the -W option. For example, to ignore warnings, use the following command −
python3 -W ignore script.py
Other options are listed below −
| default | Prints each warning once per source line (default behavior). |
| all | Prints a warning every time it occurs, even repeatedly on the same line. |
| module | Prints each warning only the first time it occurs in each module. |
| once | Prints each warning only the first time it occurs in the program. |
| error | Raises an exception instead of printing a warning. |
Displaying the Imported Modules
To display the imported modules in the script, use the -v option −
python3 -v script.py
To increase the verbosity level, use the -vv −
python3 -vv script.py
Displaying Help for Python Environment Variables
To display the help for the Python environment variables, use the --help-env option −
python3 --help-env
Displaying Usage Help
To display the usage help of the python command, use the -h, -?, or --help option −
python3 -h
To display full usage help, use the --help-all option −
python3 --help-all
Conclusion
The python command in Linux is used to run Python scripts or start the interactive Python shell. It supports various options to modify execution behavior, such as running modules, enabling debugging, controlling warnings, and ignoring environment variables. Modern Linux systems default to python3, as Python 2 is deprecated.
This tutorial covered the syntax, available options, and practical usage examples of the python command, providing insights into its flexibility for scripting, automation, and development.