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Execute Python Code

There are multiple ways to execute a Python code.

Interactive Mode

  • Enter Python interactive mode, just by running python at the command line (Make sure the PATH environment variable is updated with Python’s path).
  • You can execute statements and get the results instantly, in this mode. The code is converted into machine code and executed by the Interpreter on the fly.
  • The data (for example, variable values) persists within the session and can be reused in the subsequent statements.
  • This is referred to as REPL, short for Read, Eval, Print & Loop.

IDLE

  • IDLE is the Intergrated Development Environment (IDE) that comes pre-installed with Python’s installation. It can also be used to interact with the Python interpreter.

Using a File

  • The problem with interactive mode is that the code executed is lost after the session gets closed. If you want to execute a specific piece of code again & again, it’s better to keep it in a file.
  • These files are called modules in Python and they are discussed in later part of this book.
  • To execute the code in the file, simply pass the file path as an argument to the python command. Ex: python filename.py
  • You can also include shebang in the file (#! /usr/local/bin/python) to provide Python location and execute the file directly as ./filename.py, without the need for python command.
    • Make sure necessary permissions (chmod 755) are added to the file, to make it executable.
    • If you aren’t sure about the python location and would want to rely on PATH env variable to find it, you can change the shebang to #! /usr/bin/env python (Change the path of env utility if needed. It's usually found in /bin or /usr/bin or /usr/local/bin or /usr/sbin).

Other Methods

  • There are, of course, other methods to execute Python statements. You can use advanced IDEs such as PyCharm, to manage your python packages.
  • You can also embed Python interpreter into C or C++ applications, and therefore execute Python statements. This is a bit advanced and isn’t covered in this documentation (May be later).