Programming Python, 3rd Edition

3.1. "The os.path to Knowledge" This chapter begins our in-depth look at ways to apply Python to real programming tasks. In this and the following chapters, you'll see how to use Python to write system tools, GUIs, database applications, Intern...

3.2. System Scripting Overview We will take a quick tour through the standard library sys and os modules in the first few sections of this chapter before moving on to larger system programming concepts. As you can tell from the length of their att...

3.3. Introducing the sys Module On to module details; as mentioned earlier, the sys and os modules form the core of much of Python's system-related tool set. Let's now take a quick, interactive tour through some of the tools in these two modules b...

3.4. Introducing the os Module As mentioned, os is the larger of the two core system modules. It contains all of the usual operating-system calls you may have used in your C programs and shell scripts. Its calls deal with directories, process...

3.5. Script Execution Context Python scripts don't run in a vacuum. Depending on platforms and startup procedures, Python programs may have all sorts of enclosing context; information automatically passed in to the program by the operat...

3.6. Current Working Directory The notion of the current working directory (CWD) turns out to be a key concept in some scripts' execution: it's always the implicit place where files processed by the script are assumed to reside unless t...

3.7. Command-Line Arguments The sys module is also where Python makes available the words typed on the command that is used to start a Python script. These words are usually referred to as command-line arguments and show up in sys.ar...

3.8. Shell Environment Variables Shell variables, sometimes known as environment variables, are made available to Python scripts as os.environ, a Python dictionary-like object with one entry per variable setting in the shell. Shell variables ...

3.9. Standard Streams The sys module is also the place where the standard input, output, and error streams of your Python programs live: >>> for f in (sys.stdin, sys.stdout, sys.stderr): print f <open file '<stdin>...